diff --git a/src/diffpy/srreal/tests/testpairquantity.py b/src/diffpy/srreal/tests/testpairquantity.py
index 3ff606fc..c54c27e9 100644
--- a/src/diffpy/srreal/tests/testpairquantity.py
+++ b/src/diffpy/srreal/tests/testpairquantity.py
@@ -5,6 +5,7 @@
 
 import unittest
 import pickle
+import numpy
 
 from diffpy.srreal.pairquantity import PairQuantity
 from diffpy.srreal.srreal_ext import BasePairQuantity
@@ -76,6 +77,22 @@ def test_setStructure(self):
         return
 
 
+    def test_setPairMask_args(self):
+        """check argument type handling in setPairMask
+        """
+        spm = self.pq.setPairMask
+        gpm = self.pq.getPairMask
+        self.assertRaises(TypeError, spm, 0.0, 0, False)
+        self.assertRaises(TypeError, spm, numpy.complex(0.5), 0, False)
+        self.assertTrue(gpm(0, 0))
+        spm(numpy.int32(1), 0, True, others=False)
+        self.assertTrue(gpm(0, 1))
+        self.assertTrue(gpm(1, 0))
+        self.assertFalse(gpm(0, 0))
+        self.assertFalse(gpm(2, 7))
+        return
+
+
     def test_getStructure(self):
         """check PairQuantity.getStructure()
         """
diff --git a/src/extensions/srreal_converters.cpp b/src/extensions/srreal_converters.cpp
index 49dc183e..4fefe4a7 100644
--- a/src/extensions/srreal_converters.cpp
+++ b/src/extensions/srreal_converters.cpp
@@ -31,6 +31,7 @@
 #include <diffpy/srreal/StructureAdapter.hpp>
 
 #include "srreal_converters.hpp"
+#include "srreal_validators.hpp"
 
 #include "srreal_numpy_symbol.hpp"
 // numpy/arrayobject.h needs to be included after srreal_numpy_symbol.hpp,
@@ -73,19 +74,6 @@ boost::python::object newNumPyArray(int dim, const int* sz, int typenum)
     return rv;
 }
 
-
-bool isiterable(boost::python::object obj)
-{
-    using namespace boost::python;
-#if PY_MAJOR_VERSION >= 3
-    object Iterable = import("collections.abc").attr("Iterable");
-#else
-    object Iterable = import("collections").attr("Iterable");
-#endif
-    bool rv = (1 == PyObject_IsInstance(obj.ptr(), Iterable.ptr()));
-    return rv;
-}
-
 }   // namespace
 
 namespace srrealmodule {
@@ -304,6 +292,7 @@ int extractint(boost::python::object obj)
     if (PyArray_CheckScalar(pobj))
     {
         int rv = PyArray_PyIntAsInt(pobj);
+        if (rv == -1 && PyErr_Occurred())  python::throw_error_already_set();
         return rv;
     }
     // nothing worked, call geti which will raise an exception
diff --git a/src/extensions/srreal_validators.cpp b/src/extensions/srreal_validators.cpp
index 50742d06..4a3cb217 100644
--- a/src/extensions/srreal_validators.cpp
+++ b/src/extensions/srreal_validators.cpp
@@ -17,6 +17,7 @@
 *****************************************************************************/
 
 #include <boost/python/errors.hpp>
+#include <boost/python/import.hpp>
 
 #include "srreal_validators.hpp"
 
@@ -43,6 +44,19 @@ void ensure_non_negative(int value)
     }
 }
 
+
+bool isiterable(boost::python::object obj)
+{
+    using boost::python::import;
+#if PY_MAJOR_VERSION >= 3
+    object Iterable = import("collections.abc").attr("Iterable");
+#else
+    object Iterable = import("collections").attr("Iterable");
+#endif
+    bool rv = (1 == PyObject_IsInstance(obj.ptr(), Iterable.ptr()));
+    return rv;
+}
+
 }   // namespace srrealmodule
 
 // End of file
diff --git a/src/extensions/srreal_validators.hpp b/src/extensions/srreal_validators.hpp
index ef703e60..f123498f 100644
--- a/src/extensions/srreal_validators.hpp
+++ b/src/extensions/srreal_validators.hpp
@@ -23,6 +23,7 @@ namespace srrealmodule {
 
 void ensure_index_bounds(int idx, int lo, int hi);
 void ensure_non_negative(int value);
+bool isiterable(boost::python::object obj);
 
 }   // namespace srrealmodule
 
diff --git a/src/extensions/wrap_PairQuantity.cpp b/src/extensions/wrap_PairQuantity.cpp
index d9fda7f7..d3403ce5 100644
--- a/src/extensions/wrap_PairQuantity.cpp
+++ b/src/extensions/wrap_PairQuantity.cpp
@@ -39,6 +39,7 @@
 
 #include "srreal_converters.hpp"
 #include "srreal_pickling.hpp"
+#include "srreal_validators.hpp"
 
 #include <diffpy/srreal/PairQuantity.hpp>
 
@@ -488,13 +489,13 @@ void set_pair_mask(PairQuantity& obj,
         python::object others)
 {
     if (!others.is_none())  mask_all_pairs(obj, others);
-    python::extract<int> geti(i);
-    python::extract<int> getj(j);
     bool mask = msk;
-    // short circuit for normal call
-    if (geti.check() && getj.check())
+    // short circuit for normal call with scalar values
+    if (!isiterable(i) && !isiterable(j))
     {
-        obj.setPairMask(geti(), getj(), mask);
+        const int i1 = extractint(i);
+        const int j1 = extractint(j);
+        obj.setPairMask(i1, j1, mask);
         return;
     }
     std::vector<int> iindices = parsepairindex(i);