diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index d31f2e386c..92d9121602 100644
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -9,7 +9,7 @@
 
 #include "sha1.h"
 
-#if defined(__i386__) || defined(__x86_64__)
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
 
 /*
  * Force usage of rol or ror by selecting the one with the smaller constant.
@@ -54,7 +54,7 @@
 
 #if defined(__i386__) || defined(__x86_64__)
   #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))
-#elif defined(__arm__)
+#elif defined(__GNUC__) && defined(__arm__)
   #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
 #else
   #define setW(x, val) (W(x) = (val))