diff --git a/lib/mprintf.c b/lib/mprintf.c
index 9d446070c6d3e26b678063d56590fa1ed8d306f5..91f10fcb0d8be8fe76cfd89593b7f517f7f24142 100644
--- a/lib/mprintf.c
+++ b/lib/mprintf.c
@@ -864,7 +864,7 @@ static int dprintf_formatf(
 	    p->flags &= (~FLAGS_ALT);
 	  }
 	  else {
-	    str = "";
+	    str = (char *)"";
 	    len = 0;
 	  }
 	}