diff --git a/src/include/c.h b/src/include/c.h
index f66c752d4a0..5b678283469 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -82,6 +82,14 @@
 #endif
 #ifdef ENABLE_NLS
 #include <libintl.h>
+#endif
+
+#ifdef __cplusplus
+extern "C++"
+{
+/* This header is used in the definition of various C++ things below. */
+#include <type_traits>
+}
 #endif
 
  /* Pull in fundamental symbols that we also expose to applications */
@@ -435,6 +443,7 @@
  * [1]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2927.htm#existing-decltype
  */
 #if defined(__cplusplus)
+#undef typeof
 #ifdef pg_cxx_typeof
 #define typeof(x) pg_cxx_typeof(x)
 #elif !defined(HAVE_CXX_TYPEOF)