diff --git a/twinstall.cpp b/twinstall.cpp
index f451ca5..fa6b859 100644
--- a/twinstall.cpp
+++ b/twinstall.cpp
@@ -198,7 +198,7 @@
 
 	void *data = mmap(NULL, finfo.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (data == MAP_FAILED) {
-		LOGINFO("has_legacy_properties: mmap (size=%zu) failed: %s!\n", finfo.st_size, strerror(errno));
+		LOGINFO("has_legacy_properties: mmap (size=%zu) failed: %s!\n", (size_t)finfo.st_size, strerror(errno));
 	} else {
 		if (memmem(data, finfo.st_size, str_to_match, len_to_match)) {
 			LOGINFO("has_legacy_properties: Found legacy property match!\n");