diff --git a/resources/codemirror.panel.js b/resources/codemirror.panel.js
index 77978921..e78122b9 100644
--- a/resources/codemirror.panel.js
+++ b/resources/codemirror.panel.js
@@ -167,6 +167,7 @@ class CodeMirrorPanel {
 		// * cdx-toggle-button--toggled-off
 		btn.className = 'cdx-toggle-button cdx-toggle-button--framed ' +
 			`cdx-toggle-button--toggled-${ checked ? 'on' : 'off' } cm-mw-panel--toggle-button`;
+		btn.type = 'button';
 		btn.dataset.checked = String( checked );
 		btn.setAttribute( 'aria-pressed', checked );
 		// The following messages may be used here:
diff --git a/tests/jest/codemirror.panel.test.js b/tests/jest/codemirror.panel.test.js
index 9bf4974c..91ede72c 100644
--- a/tests/jest/codemirror.panel.test.js
+++ b/tests/jest/codemirror.panel.test.js
@@ -75,6 +75,7 @@ describe( 'CodeMirrorPanel', () => {
 		expect( toggleButtonOn.className ).toBe(
 			'cdx-toggle-button cdx-toggle-button--framed cdx-toggle-button--toggled-on cm-mw-panel--toggle-button'
 		);
+		expect( toggleButtonOn.type ).toBe( 'button' );
 		expect( toggleButtonOn.dataset.checked ).toBe( 'true' );
 		expect( toggleButtonOn.getAttribute( 'aria-pressed' ) ).toBe( 'true' );
 		expect( toggleButtonOn.title ).toBe( 'bar' );
@@ -88,6 +89,7 @@ describe( 'CodeMirrorPanel', () => {
 		expect( toggleButtonOff.className ).toBe(
 			'cdx-toggle-button cdx-toggle-button--framed cdx-toggle-button--toggled-off cm-mw-panel--toggle-button'
 		);
+		expect( toggleButtonOff.type ).toBe( 'button' );
 		expect( toggleButtonOff.dataset.checked ).toBe( 'false' );
 		expect( toggleButtonOff.getAttribute( 'aria-pressed' ) ).toBe( 'false' );
 	} );