diff --git a/gmqcc.h b/gmqcc.h
index 7834a24..5f1bdb3 100644
--- a/gmqcc.h
+++ b/gmqcc.h
@@ -987,7 +987,7 @@ typedef struct {
 
 extern opts_cmd_t opts;
 
-#define OPTS_GENERIC(f,i)    (!! (((f)[(i)/32]) & (1<< (unsigned)((i)%32))))
+#define OPTS_GENERIC(f,i)    (!! (((f)[(i)/32]) & (1U << (unsigned)((i)%32))))
 
 #define OPTS_FLAG(i)         OPTS_GENERIC(opts.flags,        (i))
 #define OPTS_WARN(i)         OPTS_GENERIC(opts.warn,         (i))