diff --git a/libavutil/cast5.c b/libavutil/cast5.c
index 63f859886c..2309223022 100644
--- a/libavutil/cast5.c
+++ b/libavutil/cast5.c
@@ -535,6 +535,7 @@ int main(int argc, char** argv)
             }
         }
     }
+    av_free(cs);
     return err;
 }
 #endif