diff --git a/src/pkcs11/pkcs11.h b/src/pkcs11/pkcs11.h
index 1686d8d4..e61756f5 100644
--- a/src/pkcs11/pkcs11.h
+++ b/src/pkcs11/pkcs11.h
@@ -86,7 +86,7 @@ extern "C" {
 #endif
 
 
-#if CRYPTOKI_COMPAT
+#ifdef CRYPTOKI_COMPAT
   /* If we are in compatibility mode, switch all exposed names to the
      PKCS #11 variant.  There are corresponding #undefs below.  */
 
@@ -308,7 +308,7 @@ typedef unsigned long ck_object_class_t;
 #define CKO_HW_FEATURE		(5)
 #define CKO_DOMAIN_PARAMETERS	(6)
 #define CKO_MECHANISM		(7)
-#define CKO_VENDOR_DEFINED	(unsigned long) (1 << 31))
+#define CKO_VENDOR_DEFINED	((unsigned long) (1 << 31))
 
 
 typedef unsigned long ck_hw_feature_type_t;
@@ -1160,7 +1160,7 @@ struct ck_c_initialize_args
 
 /* Compatibility layer.  */
 
-#if CRYPTOKI_COMPAT
+#ifdef CRYPTOKI_COMPAT
 
 #undef CK_DEFINE_FUNCTION
 #define CK_DEFINE_FUNCTION(retval, name) retval CK_SPEC name
@@ -1329,4 +1329,4 @@ typedef struct ck_c_initialize_args *CK_C_INITIALIZE_ARGS_PTR;
 }
 #endif
 
-#endif	/* PKCS11_H */
\ No newline at end of file
+#endif	/* PKCS11_H */