diff --git a/.changeset/quiet-pens-return.md b/.changeset/quiet-pens-return.md
new file mode 100644
index 00000000000..a938ccaecca
--- /dev/null
+++ b/.changeset/quiet-pens-return.md
@@ -0,0 +1,5 @@
+---
+'@graphql-codegen/add': patch
+---
+
+The plugin output's `content` is now an empty string (`''`) instead of `null` when `placement` is `prepend` or `append`. This matches the `ComplexPluginOutput` type (`content: string`). Code that calls the plugin directly and checks `content === null` should check for an empty string instead. Generated files are unchanged.
diff --git a/packages/plugins/other/add/src/index.ts b/packages/plugins/other/add/src/index.ts
index 3f842b47ad5..375f9c0e9bf 100644
--- a/packages/plugins/other/add/src/index.ts
+++ b/packages/plugins/other/add/src/index.ts
@@ -25,7 +25,7 @@ export const plugin: PluginFunction<AddPluginConfig> = async (
   }
 
   return {
-    content: null,
+    content: '',
     [placement]: Array.isArray(content) ? content : [content],
   };
 };