diff --git a/libavcodec/parser.c b/libavcodec/parser.c
index 9fd7af6ce6..1bb5f8ced6 100644
--- a/libavcodec/parser.c
+++ b/libavcodec/parser.c
@@ -261,7 +261,9 @@ int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_s
         if(!new_buffer)
             return AVERROR(ENOMEM);
         pc->buffer = new_buffer;
-        memcpy(&pc->buffer[pc->index], *buf, next + FF_INPUT_BUFFER_PADDING_SIZE );
+        if (next > -FF_INPUT_BUFFER_PADDING_SIZE)
+            memcpy(&pc->buffer[pc->index], *buf,
+                   next + FF_INPUT_BUFFER_PADDING_SIZE);
         pc->index = 0;
         *buf= pc->buffer;
     }