diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index 055107a..cb7d726 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -87,7 +87,9 @@
 {
     int nr;                     /*!< The number of rounds. */
     uint32_t *rk;               /*!< AES round keys. */
+#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES)
     uint32_t frk[8];            /*!< Fake AES round keys. */
+#endif
 #if defined(MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH) && !defined(MBEDTLS_PADLOCK_C)
     uint32_t buf[44];           /*!< Unaligned data buffer */
 #else /* MBEDTLS_AES_ONLY_128_BIT_KEY_LENGTH */