diff --git a/runtime/src/sandbox.c b/runtime/src/sandbox.c
index c9028aa..3b7b7d5 100644
--- a/runtime/src/sandbox.c
+++ b/runtime/src/sandbox.c
@@ -181,7 +181,7 @@ sandbox_alloc(struct module *module, struct http_session *session, struct route
               uint64_t admissions_estimate)
 {
 	size_t alignment     = (size_t)PAGE_SIZE;
-	size_t size_to_alloc = (size_t)round_up_to_page(sizeof(struct module));
+	size_t size_to_alloc = (size_t)round_up_to_page(sizeof(struct sandbox));
 
 	assert(size_to_alloc % alignment == 0);