diff --git a/boot/bootutil/src/image_rsa.c b/boot/bootutil/src/image_rsa.c
index 7773299..aade44e 100644
--- a/boot/bootutil/src/image_rsa.c
+++ b/boot/bootutil/src/image_rsa.c
@@ -32,7 +32,7 @@
 
 #include "bootutil_priv.h"
 
-#if MCUBOOT_RSA_PKCS1_15
+#ifdef  MCUBOOT_RSA_PKCS1_15
 static const uint8_t sha256_oid[] = {
     0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
     0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,