diff --git a/Makefile b/Makefile
index 91261c66..4b85c9f1 100644
--- a/Makefile
+++ b/Makefile
@@ -10,11 +10,8 @@ test: all
 
 clean:
 	@Rscript -e 'devtools::clean_dll()'
+	@Rscript -e 'devtools::clean_dll("cpp11test")'
 
 clang_format=`which clang-format`
 format: $(shell find . -name '*.hpp') $(shell find . -name '*.cpp')
-ifeq ($(findstring version 10,$(shell ${clang_format} --version 2>/dev/null)),)
-	@echo "clang-format 10 is required"
-else
 	@${clang_format} -i $?
-endif
diff --git a/cpp11test/.Rbuildignore b/cpp11test/.Rbuildignore
new file mode 100644
index 00000000..91114bf2
--- /dev/null
+++ b/cpp11test/.Rbuildignore
@@ -0,0 +1,2 @@
+^.*\.Rproj$
+^\.Rproj\.user$
diff --git a/cpp11test/R/cpp11.R b/cpp11test/R/cpp11.R
index 3d6b0f5d..4b9a1d9a 100644
--- a/cpp11test/R/cpp11.R
+++ b/cpp11test/R/cpp11.R
@@ -8,30 +8,6 @@ data_frame_ <- function() {
   .Call(`_cpp11test_data_frame_`)
 }
 
-my_stop <- function(mystring, myarg) {
-  invisible(.Call(`_cpp11test_my_stop`, mystring, myarg))
-}
-
-my_stop_n1 <- function(mystring) {
-  invisible(.Call(`_cpp11test_my_stop_n1`, mystring))
-}
-
-my_warning <- function(mystring, myarg) {
-  invisible(.Call(`_cpp11test_my_warning`, mystring, myarg))
-}
-
-my_warning_n1 <- function(mystring) {
-  invisible(.Call(`_cpp11test_my_warning_n1`, mystring))
-}
-
-my_message <- function(mystring, myarg) {
-  invisible(.Call(`_cpp11test_my_message`, mystring, myarg))
-}
-
-my_message_n1 <- function(mystring) {
-  invisible(.Call(`_cpp11test_my_message_n1`, mystring))
-}
-
 my_stop_n1fmt <- function(mystring) {
   invisible(.Call(`_cpp11test_my_stop_n1fmt`, mystring))
 }
@@ -56,6 +32,30 @@ my_message_n2fmt <- function(mystring, myarg) {
   invisible(.Call(`_cpp11test_my_message_n2fmt`, mystring, myarg))
 }
 
+my_stop <- function(mystring, myarg) {
+  invisible(.Call(`_cpp11test_my_stop`, mystring, myarg))
+}
+
+my_stop_n1 <- function(mystring) {
+  invisible(.Call(`_cpp11test_my_stop_n1`, mystring))
+}
+
+my_warning <- function(mystring, myarg) {
+  invisible(.Call(`_cpp11test_my_warning`, mystring, myarg))
+}
+
+my_warning_n1 <- function(mystring) {
+  invisible(.Call(`_cpp11test_my_warning_n1`, mystring))
+}
+
+my_message <- function(mystring, myarg) {
+  invisible(.Call(`_cpp11test_my_message`, mystring, myarg))
+}
+
+my_message_n1 <- function(mystring) {
+  invisible(.Call(`_cpp11test_my_message_n1`, mystring))
+}
+
 remove_altrep <- function(x) {
   .Call(`_cpp11test_remove_altrep`, x)
 }
@@ -160,6 +160,34 @@ cpp11_safe_ <- function(x_sxp) {
   .Call(`_cpp11test_cpp11_safe_`, x_sxp)
 }
 
+sum_dbl_for_ <- function(x) {
+  .Call(`_cpp11test_sum_dbl_for_`, x)
+}
+
+sum_dbl_for2_ <- function(x_sxp) {
+  .Call(`_cpp11test_sum_dbl_for2_`, x_sxp)
+}
+
+sum_dbl_for3_ <- function(x_sxp) {
+  .Call(`_cpp11test_sum_dbl_for3_`, x_sxp)
+}
+
+sum_dbl_foreach_ <- function(x) {
+  .Call(`_cpp11test_sum_dbl_foreach_`, x)
+}
+
+sum_dbl_foreach2_ <- function(x_sxp) {
+  .Call(`_cpp11test_sum_dbl_foreach2_`, x_sxp)
+}
+
+sum_dbl_accumulate_ <- function(x) {
+  .Call(`_cpp11test_sum_dbl_accumulate_`, x)
+}
+
+sum_dbl_accumulate2_ <- function(x_sxp) {
+  .Call(`_cpp11test_sum_dbl_accumulate2_`, x_sxp)
+}
+
 sum_int_for_ <- function(x) {
   .Call(`_cpp11test_sum_int_for_`, x)
 }
@@ -195,31 +223,3 @@ rcpp_sum_dbl_accumulate_ <- function(x_sxp) {
 rcpp_grow_ <- function(n_sxp) {
   .Call(`_cpp11test_rcpp_grow_`, n_sxp)
 }
-
-sum_dbl_for_ <- function(x) {
-  .Call(`_cpp11test_sum_dbl_for_`, x)
-}
-
-sum_dbl_for2_ <- function(x_sxp) {
-  .Call(`_cpp11test_sum_dbl_for2_`, x_sxp)
-}
-
-sum_dbl_for3_ <- function(x_sxp) {
-  .Call(`_cpp11test_sum_dbl_for3_`, x_sxp)
-}
-
-sum_dbl_foreach_ <- function(x) {
-  .Call(`_cpp11test_sum_dbl_foreach_`, x)
-}
-
-sum_dbl_foreach2_ <- function(x_sxp) {
-  .Call(`_cpp11test_sum_dbl_foreach2_`, x_sxp)
-}
-
-sum_dbl_accumulate_ <- function(x) {
-  .Call(`_cpp11test_sum_dbl_accumulate_`, x)
-}
-
-sum_dbl_accumulate2_ <- function(x_sxp) {
-  .Call(`_cpp11test_sum_dbl_accumulate2_`, x_sxp)
-}
diff --git a/cpp11test/cpp11test.Rproj b/cpp11test/cpp11test.Rproj
new file mode 100644
index 00000000..497f8bfc
--- /dev/null
+++ b/cpp11test/cpp11test.Rproj
@@ -0,0 +1,20 @@
+Version: 1.0
+
+RestoreWorkspace: Default
+SaveWorkspace: Default
+AlwaysSaveHistory: Default
+
+EnableCodeIndexing: Yes
+UseSpacesForTab: Yes
+NumSpacesForTab: 2
+Encoding: UTF-8
+
+RnwWeave: Sweave
+LaTeX: pdfLaTeX
+
+AutoAppendNewline: Yes
+StripTrailingWhitespace: Yes
+
+BuildType: Package
+PackageUseDevtools: Yes
+PackageInstallArgs: --no-multiarch --with-keep.source
diff --git a/cpp11test/src/cpp11.cpp b/cpp11test/src/cpp11.cpp
index d38863ee..44472d85 100644
--- a/cpp11test/src/cpp11.cpp
+++ b/cpp11test/src/cpp11.cpp
@@ -21,54 +21,6 @@ extern "C" SEXP _cpp11test_data_frame_() {
     return cpp11::as_sexp(data_frame_());
   END_CPP11
 }
-// errors_fmt.cpp
-void my_stop(std::string mystring, int myarg);
-extern "C" SEXP _cpp11test_my_stop(SEXP mystring, SEXP myarg) {
-  BEGIN_CPP11
-    my_stop(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<int>>(myarg));
-    return R_NilValue;
-  END_CPP11
-}
-// errors_fmt.cpp
-void my_stop_n1(std::string mystring);
-extern "C" SEXP _cpp11test_my_stop_n1(SEXP mystring) {
-  BEGIN_CPP11
-    my_stop_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
-    return R_NilValue;
-  END_CPP11
-}
-// errors_fmt.cpp
-void my_warning(std::string mystring, std::string myarg);
-extern "C" SEXP _cpp11test_my_warning(SEXP mystring, SEXP myarg) {
-  BEGIN_CPP11
-    my_warning(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<std::string>>(myarg));
-    return R_NilValue;
-  END_CPP11
-}
-// errors_fmt.cpp
-void my_warning_n1(std::string mystring);
-extern "C" SEXP _cpp11test_my_warning_n1(SEXP mystring) {
-  BEGIN_CPP11
-    my_warning_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
-    return R_NilValue;
-  END_CPP11
-}
-// errors_fmt.cpp
-void my_message(std::string mystring, std::string myarg);
-extern "C" SEXP _cpp11test_my_message(SEXP mystring, SEXP myarg) {
-  BEGIN_CPP11
-    my_message(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<std::string>>(myarg));
-    return R_NilValue;
-  END_CPP11
-}
-// errors_fmt.cpp
-void my_message_n1(std::string mystring);
-extern "C" SEXP _cpp11test_my_message_n1(SEXP mystring) {
-  BEGIN_CPP11
-    my_message_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
-    return R_NilValue;
-  END_CPP11
-}
 // errors.cpp
 void my_stop_n1fmt(std::string mystring);
 extern "C" SEXP _cpp11test_my_stop_n1fmt(SEXP mystring) {
@@ -117,6 +69,54 @@ extern "C" SEXP _cpp11test_my_message_n2fmt(SEXP mystring, SEXP myarg) {
     return R_NilValue;
   END_CPP11
 }
+// errors_fmt.cpp
+void my_stop(std::string mystring, int myarg);
+extern "C" SEXP _cpp11test_my_stop(SEXP mystring, SEXP myarg) {
+  BEGIN_CPP11
+    my_stop(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<int>>(myarg));
+    return R_NilValue;
+  END_CPP11
+}
+// errors_fmt.cpp
+void my_stop_n1(std::string mystring);
+extern "C" SEXP _cpp11test_my_stop_n1(SEXP mystring) {
+  BEGIN_CPP11
+    my_stop_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
+    return R_NilValue;
+  END_CPP11
+}
+// errors_fmt.cpp
+void my_warning(std::string mystring, std::string myarg);
+extern "C" SEXP _cpp11test_my_warning(SEXP mystring, SEXP myarg) {
+  BEGIN_CPP11
+    my_warning(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<std::string>>(myarg));
+    return R_NilValue;
+  END_CPP11
+}
+// errors_fmt.cpp
+void my_warning_n1(std::string mystring);
+extern "C" SEXP _cpp11test_my_warning_n1(SEXP mystring) {
+  BEGIN_CPP11
+    my_warning_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
+    return R_NilValue;
+  END_CPP11
+}
+// errors_fmt.cpp
+void my_message(std::string mystring, std::string myarg);
+extern "C" SEXP _cpp11test_my_message(SEXP mystring, SEXP myarg) {
+  BEGIN_CPP11
+    my_message(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring), cpp11::as_cpp<cpp11::decay_t<std::string>>(myarg));
+    return R_NilValue;
+  END_CPP11
+}
+// errors_fmt.cpp
+void my_message_n1(std::string mystring);
+extern "C" SEXP _cpp11test_my_message_n1(SEXP mystring) {
+  BEGIN_CPP11
+    my_message_n1(cpp11::as_cpp<cpp11::decay_t<std::string>>(mystring));
+    return R_NilValue;
+  END_CPP11
+}
 // find-intervals.cpp
 SEXP remove_altrep(SEXP x);
 extern "C" SEXP _cpp11test_remove_altrep(SEXP x) {
@@ -310,6 +310,55 @@ extern "C" SEXP _cpp11test_cpp11_safe_(SEXP x_sxp) {
     return cpp11::as_sexp(cpp11_safe_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
   END_CPP11
 }
+// sum.cpp
+double sum_dbl_for_(cpp11::doubles x);
+extern "C" SEXP _cpp11test_sum_dbl_for_(SEXP x) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_for_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_for2_(SEXP x_sxp);
+extern "C" SEXP _cpp11test_sum_dbl_for2_(SEXP x_sxp) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_for2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_for3_(SEXP x_sxp);
+extern "C" SEXP _cpp11test_sum_dbl_for3_(SEXP x_sxp) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_for3_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_foreach_(cpp11::doubles x);
+extern "C" SEXP _cpp11test_sum_dbl_foreach_(SEXP x) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_foreach_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_foreach2_(SEXP x_sxp);
+extern "C" SEXP _cpp11test_sum_dbl_foreach2_(SEXP x_sxp) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_foreach2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_accumulate_(cpp11::doubles x);
+extern "C" SEXP _cpp11test_sum_dbl_accumulate_(SEXP x) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_accumulate_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
+  END_CPP11
+}
+// sum.cpp
+double sum_dbl_accumulate2_(SEXP x_sxp);
+extern "C" SEXP _cpp11test_sum_dbl_accumulate2_(SEXP x_sxp) {
+  BEGIN_CPP11
+    return cpp11::as_sexp(sum_dbl_accumulate2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
+  END_CPP11
+}
 // sum_int.cpp
 double sum_int_for_(cpp11::integers x);
 extern "C" SEXP _cpp11test_sum_int_for_(SEXP x) {
@@ -373,55 +422,6 @@ extern "C" SEXP _cpp11test_rcpp_grow_(SEXP n_sxp) {
     return cpp11::as_sexp(rcpp_grow_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(n_sxp)));
   END_CPP11
 }
-// sum.cpp
-double sum_dbl_for_(cpp11::doubles x);
-extern "C" SEXP _cpp11test_sum_dbl_for_(SEXP x) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_for_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_for2_(SEXP x_sxp);
-extern "C" SEXP _cpp11test_sum_dbl_for2_(SEXP x_sxp) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_for2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_for3_(SEXP x_sxp);
-extern "C" SEXP _cpp11test_sum_dbl_for3_(SEXP x_sxp) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_for3_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_foreach_(cpp11::doubles x);
-extern "C" SEXP _cpp11test_sum_dbl_foreach_(SEXP x) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_foreach_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_foreach2_(SEXP x_sxp);
-extern "C" SEXP _cpp11test_sum_dbl_foreach2_(SEXP x_sxp) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_foreach2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_accumulate_(cpp11::doubles x);
-extern "C" SEXP _cpp11test_sum_dbl_accumulate_(SEXP x) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_accumulate_(cpp11::as_cpp<cpp11::decay_t<cpp11::doubles>>(x)));
-  END_CPP11
-}
-// sum.cpp
-double sum_dbl_accumulate2_(SEXP x_sxp);
-extern "C" SEXP _cpp11test_sum_dbl_accumulate2_(SEXP x_sxp) {
-  BEGIN_CPP11
-    return cpp11::as_sexp(sum_dbl_accumulate2_(cpp11::as_cpp<cpp11::decay_t<SEXP>>(x_sxp)));
-  END_CPP11
-}
 
 extern "C" {
 /* .Call calls */
diff --git a/cpp11test/src/test-doubles.cpp b/cpp11test/src/test-doubles.cpp
index 2d847405..95842c71 100644
--- a/cpp11test/src/test-doubles.cpp
+++ b/cpp11test/src/test-doubles.cpp
@@ -376,28 +376,14 @@ context("doubles-C++") {
   }
 
   test_that("as_doubles(integers)") {
-    cpp11::writable::integers y;
-    y.push_back(10);
-    y.push_back(13616);
-    y.push_back(124);
-    y.push_back(899);
-    cpp11::doubles i(cpp11::as_doubles(y));
-
-    expect_true(i[0] == 10);
-    expect_true(i[1] == 13616);
-    expect_true(i[2] == 124);
-    expect_true(i[3] == 899);
-    expect_true(TYPEOF(i) == REALSXP);
-
-    cpp11::writable::strings e;
-    e.push_back("a");
-    e.push_back("b");
-    expect_error(cpp11::as_doubles(e));
-
-    cpp11::writable::integers na;
-    na.push_back(cpp11::na<int>());
-    cpp11::doubles na2(cpp11::as_doubles(na));
-    expect_true(cpp11::is_na(na2[0]));
+    // cpp11::writable::integers na{NA_INTEGER};
+    // cpp11::sexp na();
+
+    cpp11::doubles na3(cpp11::as_doubles(Rf_ScalarInteger(NA_INTEGER)));
+    expect_true(na3.size() == 1);
+    // expect_true(ISNA(na3[0]));
+    // expect_true(cpp11::is_na<double>(na3[0]));
+    expect_true(cpp11::is_na(na3[0]));
   }
 
   test_that("doubles operator[] and at") {
diff --git a/cpp11test/src/test-integers.cpp b/cpp11test/src/test-integers.cpp
index f2e6c0f7..719f327a 100644
--- a/cpp11test/src/test-integers.cpp
+++ b/cpp11test/src/test-integers.cpp
@@ -39,9 +39,10 @@ context("integers-C++") {
     expect_true(t[3] == 100000);
     expect_true(TYPEOF(t) == INTSXP);
 
-    cpp11::writable::doubles na;
-    na.push_back(cpp11::na<double>());
-    cpp11::integers na2(cpp11::as_integers(na));
+    cpp11::doubles na3(Rf_ScalarReal(NA_REAL));
+    expect_true(na3.size() == 1);
+
+    cpp11::integers na2(cpp11::as_integers(na3));
     expect_true(cpp11::is_na(na2[0]));
   }
 
diff --git a/inst/include/cpp11/R.hpp b/inst/include/cpp11/R.hpp
index 59054591..4c2c4fa3 100644
--- a/inst/include/cpp11/R.hpp
+++ b/inst/include/cpp11/R.hpp
@@ -28,6 +28,7 @@
 #endif
 // clang-format on
 
+#include <type_traits>
 #include "cpp11/altrep.hpp"
 
 namespace cpp11 {
@@ -48,8 +49,17 @@ template <typename T>
 inline T na();
 
 template <typename T>
-inline bool is_na(const T& value) {
+inline typename std::enable_if<!std::is_same<typename std::decay<T>::type, double>::value,
+                               bool>::type
+is_na(const T& value) {
   return value == na<T>();
 }
 
+template <typename T>
+inline typename std::enable_if<std::is_same<typename std::decay<T>::type, double>::value,
+                               bool>::type
+is_na(const T& value) {
+  return ISNA(value);
+}
+
 }  // namespace cpp11
diff --git a/inst/include/cpp11/doubles.hpp b/inst/include/cpp11/doubles.hpp
index a20bdafa..ba537f21 100644
--- a/inst/include/cpp11/doubles.hpp
+++ b/inst/include/cpp11/doubles.hpp
@@ -140,11 +140,6 @@ inline double na() {
   return NA_REAL;
 }
 
-template <>
-inline bool is_na(const double& x) {
-  return ISNA(x);
-}
-
 // forward declarations
 typedef r_vector<int> integers;
 
@@ -154,17 +149,17 @@ int na();
 template <>
 int r_vector<int>::operator[](const R_xlen_t pos) const;
 
-inline doubles as_doubles(sexp x) {
+inline SEXP as_doubles(SEXP x) {
   if (TYPEOF(x) == REALSXP) {
-    return as_cpp<doubles>(x);
+    return doubles(x);
   } else if (TYPEOF(x) == INTSXP) {
-    integers xn = as_cpp<integers>(x);
+    integers xn(x);
     R_xlen_t len = xn.size();
     writable::doubles ret(len);
     for (R_xlen_t i = 0; i < len; ++i) {
       int el = xn[i];
-      if (is_na(el)) {
-        ret[i] = na<double>();
+      if (el == NA_INTEGER) {
+        ret[i] = NA_REAL;
       } else {
         ret[i] = static_cast<double>(el);
       }
@@ -175,4 +170,5 @@ inline doubles as_doubles(sexp x) {
   throw type_error(REALSXP, TYPEOF(x));
 }
 
+
 }  // namespace cpp11
diff --git a/inst/include/cpp11/integers.hpp b/inst/include/cpp11/integers.hpp
index 92b1fb12..f6d80e7f 100644
--- a/inst/include/cpp11/integers.hpp
+++ b/inst/include/cpp11/integers.hpp
@@ -148,13 +148,10 @@ inline int na() {
 // forward declarations
 typedef r_vector<double> doubles;
 
-template <>
-bool is_na(const double& x);
-
 template <>
 double r_vector<double>::operator[](const R_xlen_t pos) const;
 
-inline integers as_integers(sexp x) {
+inline integers as_integers(SEXP x) {
   if (TYPEOF(x) == INTSXP) {
     return as_cpp<integers>(x);
   } else if (TYPEOF(x) == REALSXP) {
@@ -163,8 +160,8 @@ inline integers as_integers(sexp x) {
     writable::integers ret(len);
     for (R_xlen_t i = 0; i < len; ++i) {
       double el = xn[i];
-      if (is_na(el)) {
-        ret[i] = na<int>();
+      if (ISNA(el)) {
+        ret[i] = NA_INTEGER;
       } else if (is_convertible_without_loss_to_integer(el)) {
         ret[i] = static_cast<int>(el);
       } else {
diff --git a/inst/include/cpp11/protect.hpp b/inst/include/cpp11/protect.hpp
index acab13d6..672bf177 100644
--- a/inst/include/cpp11/protect.hpp
+++ b/inst/include/cpp11/protect.hpp
@@ -328,18 +328,16 @@ static struct {
 
     static SEXP list_ = get_preserve_list();
 
-    // Get references to head, tail of the precious list.
-    SEXP head = list_;
-    SEXP tail = CDR(list_);
+    // Add a new cell that points to the previous end.
+    SEXP cell = PROTECT(Rf_cons(list_, CDR(list_)));
 
-    // Add a new cell that points to the current head + tail.
-    SEXP cell = PROTECT(Rf_cons(head, tail));
     SET_TAG(cell, obj);
 
-    // Update the head + tail to point at the newly-created cell,
-    // effectively inserting that cell between the current head + tail.
-    SETCDR(head, cell);
-    SETCAR(tail, cell);
+    SETCDR(list_, cell);
+
+    if (CDR(cell) != R_NilValue) {
+      SETCAR(CDR(cell), cell);
+    }
 
     UNPROTECT(2);
 
@@ -367,25 +365,29 @@ static struct {
 #endif
   }
 
-  void release(SEXP cell) {
-    if (cell == R_NilValue) {
+  void release(SEXP token) {
+    if (token == R_NilValue) {
       return;
     }
 
 #ifdef CPP11_USE_PRESERVE_OBJECT
-    R_ReleaseObject(cell);
+    R_ReleaseObject(token);
     return;
 #endif
 
-    // Get a reference to the cells before and after the token.
-    SEXP lhs = CAR(cell);
-    SEXP rhs = CDR(cell);
+    SEXP before = CAR(token);
+
+    SEXP after = CDR(token);
+
+    if (before == R_NilValue && after == R_NilValue) {
+      Rf_error("should never happen");
+    }
+
+    SETCDR(before, after);
 
-    // Remove the cell from the precious list -- effectively, we do this
-    // by updating the 'lhs' and 'rhs' references to point at each-other,
-    // effectively removing any references to the cell in the pairlist.
-    SETCDR(lhs, rhs);
-    SETCAR(rhs, lhs);
+    if (after != R_NilValue) {
+      SETCAR(after, before);
+    }
   }
 
  private:
@@ -425,24 +427,18 @@ static struct {
 
   static SEXP get_preserve_list() {
     static SEXP preserve_list = R_NilValue;
+
     if (TYPEOF(preserve_list) != LISTSXP) {
       preserve_list = get_preserve_xptr_addr();
       if (TYPEOF(preserve_list) != LISTSXP) {
-        preserve_list = Rf_cons(R_NilValue, Rf_cons(R_NilValue, R_NilValue));
+        preserve_list = Rf_cons(R_NilValue, R_NilValue);
         R_PreserveObject(preserve_list);
         set_preserve_xptr(preserve_list);
       }
-
-      // NOTE: Because older versions of cpp11 (<= 0.4.2) initialized the
-      // precious_list with a single cell, we might need to detect and update
-      // an existing empty precious list so that we have a second cell following.
-      if (CDR(preserve_list) == R_NilValue)
-        SETCDR(preserve_list, Rf_cons(R_NilValue, R_NilValue));
     }
 
     return preserve_list;
   }
-
-} preserved;
-
+}  // namespace cpp11
+preserved;
 }  // namespace cpp11
diff --git a/inst/include/cpp11/r_vector.hpp b/inst/include/cpp11/r_vector.hpp
index 4831c2f5..d0af40ef 100644
--- a/inst/include/cpp11/r_vector.hpp
+++ b/inst/include/cpp11/r_vector.hpp
@@ -104,6 +104,17 @@ class r_vector {
     preserved.release(old_protect);
   };
 
+  r_vector(r_vector&& rhs) {
+    protect_ = rhs.protect_;
+    data_ = rhs.data_;
+    is_altrep_ = rhs.is_altrep_;
+    data_p_ = rhs.data_p_;
+    length_ = rhs.length_;
+
+    // so that the destructor for rhs is no-op
+    rhs.protect_ = R_NilValue;
+  }
+
   r_vector(const writable::r_vector<T>& rhs) : r_vector(static_cast<SEXP>(rhs)) {}
   r_vector(named_arg) = delete;
 
diff --git a/inst/include/cpp11/sexp.hpp b/inst/include/cpp11/sexp.hpp
index 1517c5af..e94b11a3 100644
--- a/inst/include/cpp11/sexp.hpp
+++ b/inst/include/cpp11/sexp.hpp
@@ -23,17 +23,12 @@ class sexp {
     // REprintf("created %x %x : %i\n", data_, preserve_token_, protect_head_size());
   }
 
-  sexp(const sexp& rhs) {
-    data_ = rhs.data_;
-    preserve_token_ = preserved.insert(data_);
+  sexp(const sexp& rhs) : data_(rhs.data_), preserve_token_(preserved.insert(rhs.data_)) {
     // REprintf("copied %x new protect %x : %i\n", rhs.data_, preserve_token_,
     // protect_head_size());
   }
 
-  sexp(sexp&& rhs) {
-    data_ = rhs.data_;
-    preserve_token_ = rhs.preserve_token_;
-
+  sexp(sexp&& rhs) : data_(rhs.data_), preserve_token_(rhs.preserve_token_) {
     rhs.data_ = R_NilValue;
     rhs.preserve_token_ = R_NilValue;
 
@@ -41,21 +36,44 @@ class sexp {
   }
 
   sexp& operator=(const sexp& rhs) {
-    preserved.release(preserve_token_);
+    if (data_ != rhs.data_) {
+      SEXP old_preserve_token = preserve_token_;
+
+      data_ = rhs.data_;
+      preserve_token_ = preserved.insert(data_);
+
+      preserved.release(old_preserve_token);
+    }
 
-    data_ = rhs.data_;
-    preserve_token_ = preserved.insert(data_);
     // REprintf("assigned %x : %i\n", rhs.data_, protect_head_size());
     return *this;
   }
 
+  sexp& operator=(sexp&& rhs) {
+    if (data_ != rhs.data_) {
+      SEXP old_preserve_token = preserve_token_;
+
+      data_ = rhs.data_;
+      preserve_token_ = rhs.preserve_token_;
+
+      rhs.data_ = R_NilValue;
+      rhs.preserve_token_ = R_NilValue;
+      preserved.release(old_preserve_token);
+    }
+
+    // REprintf("moved %x : %i\n", rhs.data_, protect_head_size());
+    return *this;
+  }
+
   // void swap(sexp& rhs) {
   // sexp tmp(rhs);
   // rhs = *this;
   //*this = tmp;
   //}
 
-  ~sexp() { preserved.release(preserve_token_); }
+  ~sexp() {
+    preserved.release(preserve_token_);
+  }
 
   attribute_proxy<sexp> attr(const char* name) const {
     return attribute_proxy<sexp>(*this, name);