diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 20294553a5dd..2840924ec976 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -1657,7 +1657,7 @@ TEST_F(hmm2, double_map)
 
 	buffer->fd = -1;
 	buffer->size = size;
-	buffer->mirror = malloc(npages);
+	buffer->mirror = malloc(size);
 	ASSERT_NE(buffer->mirror, NULL);
 
 	/* Reserve a range of addresses. */