diff --git a/browser/themes/osx/browser.css b/browser/themes/osx/browser.css
index 181b039fd68..3057593293f 100644
--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -1405,6 +1405,7 @@ toolbarbutton.bookmark-item > menupopup {
 }
 
 #zoom-controls[cui-areatype="toolbar"] > #zoom-reset-button {
+  min-width: 0;
   margin: 0;
 }
 
diff --git a/browser/themes/shared/customizableui/panelUIOverlay.inc.css b/browser/themes/shared/customizableui/panelUIOverlay.inc.css
index a2d2833814e..d62ddf8d7b0 100644
--- a/browser/themes/shared/customizableui/panelUIOverlay.inc.css
+++ b/browser/themes/shared/customizableui/panelUIOverlay.inc.css
@@ -413,7 +413,11 @@ toolbarbutton.panel-multiview-anchor {
 }
 
 #zoom-controls[cui-areatype="toolbar"] > #zoom-reset-button > .toolbarbutton-text {
-  min-width: 4em;
+%ifdef XP_MACOSX
+  min-width: 6ch;
+%else
+  min-width: 7ch;
+%endif
 }
 
 #zoom-controls@inAnyPanel@ > #zoom-reset-button {