diff --git a/tools/convbdf.c b/tools/convbdf.c
index 010e8ee2c2..aae5b4302d 100644
--- a/tools/convbdf.c
+++ b/tools/convbdf.c
@@ -102,7 +102,7 @@ usage(void)
 	"    -n     Don't generate bitmaps as comments in .c file\n"
 	};
 
-    fprintf(stderr, help);
+    fprintf(stderr, "%s", help);
 }
 
 /* parse command line options*/