diff --git a/util/kconfig/nconf.c b/util/kconfig/nconf.c
index 905dcd11bd..42ea494f6b 100644
--- a/util/kconfig/nconf.c
+++ b/util/kconfig/nconf.c
@@ -5,7 +5,9 @@
  * Derived from menuconfig.
  *
  */
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <string.h>
 #include <stdlib.h>
 
diff --git a/util/kconfig/regex.c b/util/kconfig/regex.c
index a6d947fbd0..d0e1d7b2f5 100644
--- a/util/kconfig/regex.c
+++ b/util/kconfig/regex.c
@@ -24,7 +24,9 @@
   #pragma alloca
 #endif
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 
 /* We need this for `regex.h', and perhaps for the Emacs include files.  */
 #include <sys/types.h>