diff --git a/src/crypto/fipsmodule/modes/gcm_test.cc b/src/crypto/fipsmodule/modes/gcm_test.cc
index ebcfcbeaf..fafde9c7f 100644
--- a/src/crypto/fipsmodule/modes/gcm_test.cc
+++ b/src/crypto/fipsmodule/modes/gcm_test.cc
@@ -29,7 +29,7 @@ TEST(GCMTest, ABI) {
       UINT64_C(0x884cfa59ca342b2e),
   };
   static const size_t kBlockCounts[] = {1, 2, 3, 4, 5, 6, 7, 8, 15, 16, 31, 32};
-  uint8_t buf[16 * 32];
+  uint8_t buf[16 * 32 + 7];
   OPENSSL_memset(buf, 42, sizeof(buf));
 
   uint8_t X[16] = {0x92, 0xa3, 0xb3, 0x60, 0xce, 0xda, 0x88, 0x03,