diff --git a/CHANGELOG.md b/CHANGELOG.md
index b616620..2126d09 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ### Fixed
 
 - Multiple protocols for a service now renders multiple openapi documents.
+- Format and type are now preserved for function parameters.
 
 ### Added
 
diff --git a/lib/compile/csdl2openapi.js b/lib/compile/csdl2openapi.js
index e1f7545..f1d7145 100644
--- a/lib/compile/csdl2openapi.js
+++ b/lib/compile/csdl2openapi.js
@@ -2273,9 +2273,6 @@ see [Expand](http://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-prot
                 s.pattern = "^'([^']|'')*'$";
             }
             if (element.$Nullable) {
-                if (!s.anyOf && !s.allOf) s.type = "string";
-                if (s.format) s.format += ",null";
-                if (s.anyOf && s.anyOf[0].format) s.anyOf[0].format += ",null";
                 s.default = "null";
                 if (s.pattern) {
                     s.pattern = s.pattern.replace(/^\^/, "^(null|");
diff --git a/test/lib/compile/data/csdl-16.1.openapi3.json b/test/lib/compile/data/csdl-16.1.openapi3.json
index d971421..f1733b5 100644
--- a/test/lib/compile/data/csdl-16.1.openapi3.json
+++ b/test/lib/compile/data/csdl-16.1.openapi3.json
@@ -1430,8 +1430,8 @@
             "in": "query",
             "name": "Rating",
             "schema": {
-              "type": "string",
-              "format": "int32,null",
+              "type": "integer",
+              "format": "int32",
               "nullable": true,
               "default": "null"
             }