diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
index 426dccc08..738c34eb5 100755
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -1474,7 +1474,7 @@ 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. */