diff --git a/library/gcm.c b/library/gcm.c
index fccb092..2b49fa6 100644
--- a/library/gcm.c
+++ b/library/gcm.c
@@ -54,6 +54,8 @@
 #endif /* MBEDTLS_PLATFORM_C */
 #endif /* MBEDTLS_SELF_TEST && MBEDTLS_AES_C */
 
+#if !defined(MBEDTLS_GCM_ALT)
+
 /*
  * 32-bit integer manipulation macros (big endian)
  */
@@ -508,6 +510,8 @@
     mbedtls_zeroize( ctx, sizeof( mbedtls_gcm_context ) );
 }
 
+#endif /* !MBEDTLS_GCM_ALT */
+
 #if defined(MBEDTLS_SELF_TEST) && defined(MBEDTLS_AES_C)
 /*
  * AES-GCM test vectors from:
diff --git a/library/version_features.c b/library/version_features.c
index 5cbe8ac..50afe1e 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -99,6 +99,9 @@
 #if defined(MBEDTLS_DES_ALT)
     "MBEDTLS_DES_ALT",
 #endif /* MBEDTLS_DES_ALT */
+#if defined(MBEDTLS_GCM_ALT)
+    "MBEDTLS_GCM_ALT",
+#endif /* MBEDTLS_GCM_ALT */
 #if defined(MBEDTLS_XTEA_ALT)
     "MBEDTLS_XTEA_ALT",
 #endif /* MBEDTLS_XTEA_ALT */