diff --git a/library/aes.c b/library/aes.c
index de43306..6ed0956 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -201,7 +201,7 @@
 static const uint32_t FT0[256] = { FT };
 #undef V
 
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
 
 #define V(a,b,c,d) 0x##b##c##d##a
 static const uint32_t FT1[256] = { FT };
@@ -332,7 +332,7 @@
 static const uint32_t RT0[256] = { RT };
 #undef V
 
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
 
 #define V(a,b,c,d) 0x##b##c##d##a
 static const uint32_t RT1[256] = { RT };
@@ -367,7 +367,7 @@
  */
 static unsigned char FSb[256];
 static uint32_t FT0[256];
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
 static uint32_t FT1[256];
 static uint32_t FT2[256];
 static uint32_t FT3[256];
@@ -378,7 +378,7 @@
  */
 static unsigned char RSb[256];
 static uint32_t RT0[256];
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
 static uint32_t RT1[256];
 static uint32_t RT2[256];
 static uint32_t RT3[256];
@@ -457,7 +457,7 @@
                  ( (uint32_t) x << 16 ) ^
                  ( (uint32_t) z << 24 );
 
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
         FT1[i] = ROTL8( FT0[i] );
         FT2[i] = ROTL8( FT1[i] );
         FT3[i] = ROTL8( FT2[i] );
@@ -470,7 +470,7 @@
                  ( (uint32_t) MUL( 0x0D, x ) << 16 ) ^
                  ( (uint32_t) MUL( 0x0B, x ) << 24 );
 
-#ifndef MBEDTLS_AES_FEWER_TABLES
+#if !defined(MBEDTLS_AES_FEWER_TABLES)
         RT1[i] = ROTL8( RT0[i] );
         RT2[i] = ROTL8( RT1[i] );
         RT3[i] = ROTL8( RT2[i] );
@@ -482,7 +482,7 @@
 
 #endif /* MBEDTLS_AES_ROM_TABLES */
 
-#ifdef MBEDTLS_AES_FEWER_TABLES
+#if defined(MBEDTLS_AES_FEWER_TABLES)
 
 #define ROTL8(x)  ( (uint32_t)( ( x ) <<  8 ) + (uint32_t)( ( x ) >> 24 ) )
 #define ROTL16(x) ( (uint32_t)( ( x ) << 16 ) + (uint32_t)( ( x ) >> 16 ) )