diff --git a/tools/lib/h5tools.h b/tools/lib/h5tools.h
index 129afa1e59e..ad62ebdd81e 100644
--- a/tools/lib/h5tools.h
+++ b/tools/lib/h5tools.h
@@ -21,6 +21,9 @@
 #if defined(H5_HAVE_ATTRIBUTE) && !defined(__SUNPRO_C)
 #define H5_ATTR_FORMAT(X, Y, Z) __attribute__((format(X, Y, Z)))
 #define H5_ATTR_UNUSED          __attribute__((unused))
+#else
+#   define H5_ATTR_FORMAT(X, Y, Z) /*void*/
+#   define H5_ATTR_UNUSED          /*void*/
 #endif
 
 #include "h5tools_error.h"