diff --git a/plat/mediatek/mt8173/include/platform_def.h b/plat/mediatek/mt8173/include/platform_def.h
index dc5b000..8f771e3 100644
--- a/plat/mediatek/mt8173/include/platform_def.h
+++ b/plat/mediatek/mt8173/include/platform_def.h
@@ -43,13 +43,13 @@
  ******************************************************************************/
 
 /* Size of cacheable stacks */
-#if IMAGE_BL1
+#if defined(IMAGE_BL1)
 #define PLATFORM_STACK_SIZE 0x440
-#elif IMAGE_BL2
+#elif defined(IMAGE_BL2)
 #define PLATFORM_STACK_SIZE 0x400
-#elif IMAGE_BL31
+#elif defined(IMAGE_BL31)
 #define PLATFORM_STACK_SIZE 0x800
-#elif IMAGE_BL32
+#elif defined(IMAGE_BL32)
 #define PLATFORM_STACK_SIZE 0x440
 #endif