diff --git a/libavcodec/escape124.c b/libavcodec/escape124.c
index 50fa882255..5e4e57bf90 100644
--- a/libavcodec/escape124.c
+++ b/libavcodec/escape124.c
@@ -157,7 +157,7 @@ static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
 
     // This condition can occur with invalid bitstreams and
     // *codebook_index == 2
-    if (block_index >= s->codebooks[*codebook_index].size)
+    if (block_index >= s->codebooks[*codebook_index].size || !s->codebooks[*codebook_index].blocks)
         return (MacroBlock) { { 0 } };
 
     return s->codebooks[*codebook_index].blocks[block_index];