diff --git a/assemblers/org.osbuild.qemu b/assemblers/org.osbuild.qemu
index 22cec419..8dcf6900 100755
--- a/assemblers/org.osbuild.qemu
+++ b/assemblers/org.osbuild.qemu
@@ -127,7 +127,7 @@ STAGE_OPTS = """
   },
   "size": {
     "description": "Virtual disk size",
-    "type": "string"
+    "type": "integer"
   },
   "root_fs_type": {
     "description": "Type of the root filesystem",