diff --git a/library/aes.c b/library/aes.c
index d2687bcf3d..6ec4d78086 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -1128,7 +1128,8 @@ typedef unsigned char mbedtls_be128[16];
  * for machine endianness and hence works correctly on both big and little
  * endian machines.
  */
-static void mbedtls_gf128mul_x_ble(unsigned char r[16],
+MBEDTLS_OPTIMIZE_ALWAYS
+static inline void mbedtls_gf128mul_x_ble(unsigned char r[16],
                                    const unsigned char x[16])
 {
     uint64_t a, b, ra, rb;
@@ -1145,7 +1146,11 @@ static void mbedtls_gf128mul_x_ble(unsigned char r[16],
 
 /*
  * AES-XTS buffer encryption/decryption
+ *
+ * Use of MBEDTLS_OPTIMIZE_ALWAYS here and for mbedtls_gf128mul_x_ble()
+ * is a 3x performance improvement for gcc -Os!
  */
+MBEDTLS_OPTIMIZE_ALWAYS
 int mbedtls_aes_crypt_xts(mbedtls_aes_xts_context *ctx,
                           int mode,
                           size_t length,