diff --git a/operation.go b/operation.go
index edf251002..9a02c0fd4 100644
--- a/operation.go
+++ b/operation.go
@@ -918,6 +918,10 @@ func parseCombinedObjectSchema(parser *Parser, refType string, astFile *ast.File
 				return nil, err
 			}
 
+			if schema == nil {
+				schema = PrimitiveSchema(OBJECT)
+			}
+
 			props[keyVal[0]] = *schema
 		}
 	}