diff --git a/sys/mips/include/_stdint.h b/sys/mips/include/_stdint.h
index 510b8eae32c8..ebf6eb5fcbbe 100644
--- a/sys/mips/include/_stdint.h
+++ b/sys/mips/include/_stdint.h
@@ -66,6 +66,7 @@
 
 #if !defined(__cplusplus) || defined(__STDC_LIMIT_MACROS)
 
+#ifndef __INT64_C
 #ifdef __mips_n64
 #define __INT64_C(c)              (c ## L)
 #define __UINT64_C(c)             (c ## UL)
@@ -73,6 +74,7 @@
 #define __INT64_C(c)              (c ## LL)
 #define __UINT64_C(c)             (c ## ULL)
 #endif
+#endif
 
 /*
  * ISO/IEC 9899:1999
diff --git a/sys/powerpc/include/_stdint.h b/sys/powerpc/include/_stdint.h
index 6ad1fd257d43..9928a1a0196e 100644
--- a/sys/powerpc/include/_stdint.h
+++ b/sys/powerpc/include/_stdint.h
@@ -65,6 +65,7 @@
 
 #if !defined(__cplusplus) || defined(__STDC_LIMIT_MACROS)
 
+#ifndef __INT64_C
 #ifdef __LP64__
 #define	__INT64_C(c)		(c ## L)
 #define	__UINT64_C(c)		(c ## UL)
@@ -72,6 +73,7 @@
 #define	__INT64_C(c)		(c ## LL)
 #define	__UINT64_C(c)		(c ## ULL)
 #endif
+#endif
 
 /*
  * ISO/IEC 9899:1999