diff --git a/packages/mermaid/src/mermaidAPI.spec.ts b/packages/mermaid/src/mermaidAPI.spec.ts
index 48121f36e..11c16827b 100644
--- a/packages/mermaid/src/mermaidAPI.spec.ts
+++ b/packages/mermaid/src/mermaidAPI.spec.ts
@@ -12,24 +12,24 @@ vi.mock('dagre-d3');
 
 // mermaidAPI.spec.ts:
 import * as accessibility from './accessibility.js'; // Import it this way so we can use spyOn(accessibility,...)
-vi.mock('./accessibility', () => ({
+vi.mock('./accessibility.js', () => ({
   setA11yDiagramInfo: vi.fn(),
   addSVGa11yTitleDescription: vi.fn(),
 }));
 
 // Mock the renderers specifically so we can test render(). Need to mock draw() for each renderer
-vi.mock('./diagrams/c4/c4Renderer');
-vi.mock('./diagrams/class/classRenderer');
-vi.mock('./diagrams/class/classRenderer-v2');
-vi.mock('./diagrams/er/erRenderer');
-vi.mock('./diagrams/flowchart/flowRenderer-v2');
-vi.mock('./diagrams/git/gitGraphRenderer');
-vi.mock('./diagrams/gantt/ganttRenderer');
-vi.mock('./diagrams/user-journey/journeyRenderer');
-vi.mock('./diagrams/pie/pieRenderer');
-vi.mock('./diagrams/requirement/requirementRenderer');
-vi.mock('./diagrams/sequence/sequenceRenderer');
-vi.mock('./diagrams/state/stateRenderer-v2');
+vi.mock('./diagrams/c4/c4Renderer.js');
+vi.mock('./diagrams/class/classRenderer.js');
+vi.mock('./diagrams/class/classRenderer-v2.js');
+vi.mock('./diagrams/er/erRenderer.js');
+vi.mock('./diagrams/flowchart/flowRenderer-v2.js');
+vi.mock('./diagrams/git/gitGraphRenderer.js');
+vi.mock('./diagrams/gantt/ganttRenderer.js');
+vi.mock('./diagrams/user-journey/journeyRenderer.js');
+vi.mock('./diagrams/pie/pieRenderer.js');
+vi.mock('./diagrams/requirement/requirementRenderer.js');
+vi.mock('./diagrams/sequence/sequenceRenderer.js');
+vi.mock('./diagrams/state/stateRenderer-v2.js');
 
 // -------------------------------------
 
@@ -52,7 +52,7 @@ import assignWithDepth from './assignWithDepth.js';
 // --------------
 // Mocks
 //   To mock a module, first define a mock for it, then (if used explicitly in the tests) import it. Be sure the path points to exactly the same file as is imported in mermaidAPI (the module being tested)
-vi.mock('./styles', () => {
+vi.mock('./styles.js', () => {
   return {
     addStylesForDiagram: vi.fn(),
     default: vi.fn().mockReturnValue(' .userStyle { font-weight:bold; }'),