diff --git a/libavfilter/graphdump.c b/libavfilter/graphdump.c
index 099125bea8..cf8914b558 100644
--- a/libavfilter/graphdump.c
+++ b/libavfilter/graphdump.c
@@ -29,7 +29,7 @@
 
 static int print_link_prop(AVBPrint *buf, AVFilterLink *link)
 {
-    char *format;
+    const char *format;
     AVBPrint dummy_buffer;
 
     if (!buf) {