diff --git a/src/__tests__/decodeQueryParams-test.ts b/src/__tests__/decodeQueryParams-test.ts
index 0e5a275..1225e89 100644
--- a/src/__tests__/decodeQueryParams-test.ts
+++ b/src/__tests__/decodeQueryParams-test.ts
@@ -1,10 +1,12 @@
 import { decodeQueryParams } from '../index';
+
 import {
   NumberParam,
   ArrayParam,
   StringParam,
   DelimitedArrayParam,
 } from '../params';
+import withDefault from '../withDefault';
 
 describe('decodeQueryParams', () => {
   it('works', () => {
@@ -14,6 +16,7 @@ describe('decodeQueryParams', () => {
         bar: NumberParam,
         baz: ArrayParam,
         box: DelimitedArrayParam,
+        not: withDefault(NumberParam, 94),
       },
       {
         foo: '123',
@@ -27,6 +30,7 @@ describe('decodeQueryParams', () => {
       bar: 555,
       baz: ['a', 'b', 'c'],
       box: ['a', 'b', 'c'],
+      not: 94,
     });
   });
 
diff --git a/src/decodeQueryParams.ts b/src/decodeQueryParams.ts
index b0fd54f..7bf2b6d 100644
--- a/src/decodeQueryParams.ts
+++ b/src/decodeQueryParams.ts
@@ -13,7 +13,16 @@ export function decodeQueryParams<QPCMap extends QueryParamConfigMap>(
 ): Partial<DecodedValueMap<QPCMap>> {
   const decodedQuery: Partial<DecodedValueMap<QPCMap>> = {};
 
-  const paramNames = Object.keys(encodedQuery);
+  // iterate over all keys in the config (#30)
+  const paramNames = Object.keys(paramConfigMap);
+
+  // ensure any non configured keys that are in the URL are also included
+  for (const encodedKey of Object.keys(encodedQuery)) {
+    if (paramConfigMap[encodedKey] == null) {
+      paramNames.push(encodedKey);
+    }
+  }
+
   for (const paramName of paramNames) {
     const encodedValue = encodedQuery[paramName];