diff --git a/packages/mermaid/src/diagrams/c4/c4Diagram.ts b/packages/mermaid/src/diagrams/c4/c4Diagram.ts
index d51be7160..6f8f25db2 100644
--- a/packages/mermaid/src/diagrams/c4/c4Diagram.ts
+++ b/packages/mermaid/src/diagrams/c4/c4Diagram.ts
@@ -4,8 +4,9 @@ import c4Db from './c4Db';
 import c4Renderer from './c4Renderer';
 import c4Styles from './styles';
 import { MermaidConfig } from '../../config.type';
+import { DiagramDefinition } from '../../diagram-api/types';
 
-export const diagram = {
+export const diagram: DiagramDefinition = {
   parser: c4Parser,
   db: c4Db,
   renderer: c4Renderer,