diff --git a/library/camellia.c b/library/camellia.c
index 4d6b468..29d730a 100644
--- a/library/camellia.c
+++ b/library/camellia.c
@@ -278,14 +278,14 @@
     I0 = x[0] ^ k[0];
     I1 = x[1] ^ k[1];
 
-    I0 = ((uint32_t) SBOX1((I0 >> 24) & 0xFF) << 24) |
-         ((uint32_t) SBOX2((I0 >> 16) & 0xFF) << 16) |
-         ((uint32_t) SBOX3((I0 >>  8) & 0xFF) <<  8) |
-         ((uint32_t) SBOX4((I0      ) & 0xFF)      );
-    I1 = ((uint32_t) SBOX2((I1 >> 24) & 0xFF) << 24) |
-         ((uint32_t) SBOX3((I1 >> 16) & 0xFF) << 16) |
-         ((uint32_t) SBOX4((I1 >>  8) & 0xFF) <<  8) |
-         ((uint32_t) SBOX1((I1      ) & 0xFF)      );
+    I0 = ((uint32_t) SBOX1( MBEDTLS_BYTE_3( I0 )) << 24) |
+         ((uint32_t) SBOX2( MBEDTLS_BYTE_2( I0 )) << 16) |
+         ((uint32_t) SBOX3( MBEDTLS_BYTE_1( I0 )) <<  8) |
+         ((uint32_t) SBOX4( MBEDTLS_BYTE_0( I0 ))      );
+    I1 = ((uint32_t) SBOX2( MBEDTLS_BYTE_3( I1 )) << 24) |
+         ((uint32_t) SBOX3( MBEDTLS_BYTE_2( I1 )) << 16) |
+         ((uint32_t) SBOX4( MBEDTLS_BYTE_1( I1 )) <<  8) |
+         ((uint32_t) SBOX1( MBEDTLS_BYTE_0( I1 ))      );
 
     I0 ^= (I1 << 8) | (I1 >> 24);
     I1 ^= (I0 << 16) | (I0 >> 16);