diff --git a/string/string.h b/string/string.h
index ecc3fef..bfa910c 100644
--- a/string/string.h
+++ b/string/string.h
@@ -31,8 +31,12 @@ __BEGIN_DECLS
 #define	__need_NULL
 #include <stddef.h>
 
-/* Tell the caller that we provide correct C++ prototypes.  */
-#if defined __cplusplus && __GNUC_PREREQ (4, 4)
+/* Provide correct C++ prototypes, and indicate this to the caller.  This
+   requires a compatible C++ standard library.  As a heuristic, we provide
+   these when the compiler indicates full conformance with C++97 or later,
+   and for older GCC versions that are known to provide a compatible
+   libstdc++.  */
+#if __cplusplus >= 199711L || (defined __cplusplus && __GNUC_PREREQ (4, 4))
 # define __CORRECT_ISO_CPP_STRING_H_PROTO
 #endif
 
diff --git a/string/strings.h b/string/strings.h
index dad0a04..39ccb0c 100644
--- a/string/strings.h
+++ b/string/strings.h
@@ -27,8 +27,12 @@
 # define __need_size_t
 # include <stddef.h>
 
-/* Tell the caller that we provide correct C++ prototypes.  */
-# if defined __cplusplus && __GNUC_PREREQ (4, 4)
+/* Provide correct C++ prototypes, and indicate this to the caller.  This
+   requires a compatible C++ standard library.  As a heuristic, we provide
+   these when the compiler indicates full conformance with C++97 or later,
+   and for older GCC versions that are known to provide a compatible
+   libstdc++.  */
+# if __cplusplus >= 199711L || (defined __cplusplus && __GNUC_PREREQ (4, 4))
 #  define __CORRECT_ISO_CPP_STRINGS_H_PROTO
 # endif