diff --git a/c_gen/c_code_gen.py b/c_gen/c_code_gen.py
index 735dc6d..d57f675 100644
--- a/c_gen/c_code_gen.py
+++ b/c_gen/c_code_gen.py
@@ -756,8 +756,10 @@
  *
  ****************************************************************/
 
+#if __GNUC__ >= 3
 #pragma GCC optimize ("s")
 #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#endif
 
 #include <loci/loci.h>
 #include <loci/of_object.h>