diff --git a/trove/common/apischema.py b/trove/common/apischema.py
index 554a25aa3e..882b2c88b0 100644
--- a/trove/common/apischema.py
+++ b/trove/common/apischema.py
@@ -102,7 +102,7 @@ volume = {
     "required": ["size"],
     "properties": {
         "size": volume_size,
-        "required": True
+        "type": non_empty_string
     }
 }