diff --git a/lib/gssapi/mech/mech_locl.h b/lib/gssapi/mech/mech_locl.h
index 58cf4857a..bd1f707ad 100644
--- a/lib/gssapi/mech/mech_locl.h
+++ b/lib/gssapi/mech/mech_locl.h
@@ -64,7 +64,17 @@
 #include "utils.h"
 
 #define _mg_buffer_zero(buffer) \
-	do { (buffer)->value = NULL; (buffer)->length = 0; } while(0)
+	do {					\
+		if (buffer) {			\
+			(buffer)->value = NULL;	\
+			(buffer)->length = 0;	\
+		 }				\
+	} while(0)
 
 #define _mg_oid_set_zero(oid_set) \
-	do { (oid_set)->elements = NULL; (oid_set)->length = 0; } while(0)
+	do {						\
+		if (oid_set) {				\
+			(oid_set)->elements = NULL;	\
+			 (oid_set)->length = 0;		\
+		 }					\
+	} while(0)