diff --git a/CoreFoundation/Base.subproj/CFPlatform.c b/CoreFoundation/Base.subproj/CFPlatform.c
index e54aab368a..c2ce76e800 100644
--- a/CoreFoundation/Base.subproj/CFPlatform.c
+++ b/CoreFoundation/Base.subproj/CFPlatform.c
@@ -1510,7 +1510,7 @@ void _CF_dispatch_once(dispatch_once_t *predicate, void (^block)(void)) {
 #pragma mark -
 #pragma mark Windows and Linux Helpers
 
-#if TARGET_OS_WIN32 || TARGET_OS_LINUX
+#if TARGET_OS_WIN32 || (TARGET_OS_LINUX && !defined(_GNU_SOURCE))
 
 #include <stdio.h>
 
diff --git a/CoreFoundation/Base.subproj/CoreFoundation_Prefix.h b/CoreFoundation/Base.subproj/CoreFoundation_Prefix.h
index 956b5b0524..bf6f203b5f 100644
--- a/CoreFoundation/Base.subproj/CoreFoundation_Prefix.h
+++ b/CoreFoundation/Base.subproj/CoreFoundation_Prefix.h
@@ -448,7 +448,7 @@ CF_INLINE int popcountll(long long x) {
 #define CF_TEST_PRIVATE CF_PRIVATE
 #endif
 
-#if TARGET_OS_LINUX || TARGET_OS_WIN32
+#if TARGET_OS_WIN32 || (TARGET_OS_LINUX && !defined(_GNU_SOURCE))
 
 #include <stdarg.h>