diff --git a/src/core/sys/posix/inttypes.d b/src/core/sys/posix/inttypes.d
index e2954eda5c..033eb74194 100644
--- a/src/core/sys/posix/inttypes.d
+++ b/src/core/sys/posix/inttypes.d
@@ -38,3 +38,21 @@ intmax_t  strtoimax(in char*, char**, int);
 uintmax_t strtoumax(in char *, char**, int);
 intmax_t  wcstoimax(in wchar_t*, wchar_t**, int);
 uintmax_t wcstoumax(in wchar_t*, wchar_t**, int);
+
+version (Cpp98)
+{
+}
+else
+{
+    /* Add backwards compatibility overloads to the same functions for wchar* and dchar*.
+     * Being C with no name mangling, they'll resolve to the same functions.
+     */
+    version (Windows)
+        private alias _old_wchar_t = wchar;
+    else version (Posix)
+        private alias _old_wchar_t = dchar;
+
+    intmax_t  wcstoimax(in _old_wchar_t* nptr, _old_wchar_t** endptr, int base);
+    uintmax_t wcstoumax(in _old_wchar_t* nptr, _old_wchar_t** endptr, int base);
+}
+
diff --git a/src/core/sys/posix/stdlib.d b/src/core/sys/posix/stdlib.d
index dcd302739c..a56e618e81 100644
--- a/src/core/sys/posix/stdlib.d
+++ b/src/core/sys/posix/stdlib.d
@@ -678,3 +678,22 @@ else version (CRuntime_UClibc)
     int    mkstemp(char*);
   }
 }
+
+version (Cpp98)
+{
+}
+else
+{
+    /* Add backwards compatibility overloads to the same functions for wchar* and dchar*.
+     * Being C with no name mangling, they'll resolve to the same functions.
+     */
+    version (Windows)
+        private alias _old_wchar_t = wchar;
+    else version (Posix)
+        private alias _old_wchar_t = dchar;
+
+    int     mbtowc(scope _old_wchar_t* pwc, scope const char* s, size_t n);
+    size_t  mbstowcs(scope _old_wchar_t* pwcs, scope const char* s, size_t n);
+    size_t  wcstombs(scope char* s, scope const _old_wchar_t* pwcs, size_t n);
+}
+