diff --git a/libavformat/nutdec.c b/libavformat/nutdec.c
index 10f0198092..9ecf3d4a97 100644
--- a/libavformat/nutdec.c
+++ b/libavformat/nutdec.c
@@ -501,7 +501,7 @@ static int find_and_decode_index(NUTContext *nut){
                 return -1;
             }
             assert(n<=syncpoint_count+1);
-            for(; j<n; j++){
+            for(; j<n && j<syncpoint_count; j++){
                 if(has_keyframe[j]){
                     uint64_t B, A= ff_get_v(bc);
                     if(!A){