diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 0f183e0358359e400fdcab91e1368d28bbc764fb..e8888419b5c6aef611a1610de0514faa2eb8b4ff 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -369,6 +369,10 @@ static inline uint64_t get_bits64(GetBitContext *s, int n)
  */
 static inline int get_sbits_long(GetBitContext *s, int n)
 {
+    // sign_extend(x, 0) is undefined
+    if (!n)
+        return 0;
+
     return sign_extend(get_bits_long(s, n), n);
 }