diff --git a/packages/block-library/src/heading/heading-level-dropdown.js b/packages/block-library/src/heading/heading-level-dropdown.js
index 263d0a8ba650c6..5039a30217656d 100644
--- a/packages/block-library/src/heading/heading-level-dropdown.js
+++ b/packages/block-library/src/heading/heading-level-dropdown.js
@@ -93,6 +93,15 @@ export default function HeadingLevelDropdown( { selectedLevel, onChange } ) {
 								onClick() {
 									onChange( targetLevel );
 								},
+								// Temporary workaround for macOS Firefox/Safari issue
+								// where clicking buttons in the heading level toolbar
+								// doesn't work.
+								// TODO: Replace this with a more general solution.
+								// https://github.com/WordPress/gutenberg/pull/20246#pullrequestreview-417338057
+								onMouseDown( event ) {
+									event.preventDefault();
+									event.currentTarget.focus();
+								},
 							};
 						} ) }
 					/>