diff --git a/tests/test-gguf.cpp b/tests/test-gguf.cpp
index e5b4cb7b8af1c..aba0634081bce 100644
--- a/tests/test-gguf.cpp
+++ b/tests/test-gguf.cpp
@@ -262,7 +262,7 @@ static FILE * get_handcrafted_file(const unsigned int seed, const enum handcraft
 
         size_t type_size = hft == HANDCRAFTED_KV_BAD_TYPE ? 1 : gguf_type_size(type);
         if (hft == HANDCRAFTED_KV_BAD_VALUE_SIZE) {
-            type_size += rng() % 3;
+            type_size ^= 1;
         }
         helper_write(data, type_size, file);
     }