diff --git a/src/guide/extending.md b/src/guide/extending.md
index eadbbbb3..b2e4d286 100644
--- a/src/guide/extending.md
+++ b/src/guide/extending.md
@@ -19,6 +19,10 @@ knex.ColumnBuilder.extend("functionName", function() {
     console.log('Custom Column Builder Function');
     return this;
 });
+knex.QueryBuilder.extend("functionName", function() {
+    console.log('Custom Query Builder Function');
+    return this;
+});
 ```
 
 
@@ -39,6 +43,9 @@ declare module "knex" {
         interface ColumnBuilder {
             functionName (): Knex.ColumnBuilder;
         }
+        interface QueryBuilder {
+            functionName (): Knex.QueryBuilder;
+        }
     }
 }
-```
\ No newline at end of file
+```