--- a/browser/themes/osx/devedition.css
+++ b/browser/themes/osx/devedition.css
@@ -86,20 +86,16 @@
 }
 
 #back-button:hover:active:not([disabled="true"]) {
   -moz-image-region: rect(18px, 54px, 36px, 36px);
 }
 
 /* Use smaller back button icon */
 @media (min-resolution: 2dppx) {
-  #back-button {
-    -moz-image-region: rect(0, 108px, 36px, 72px);
-  }
-
   #back-button:hover:active:not([disabled="true"]) {
     -moz-image-region: rect(36px, 108px, 72px, 72px);
   }
 }
 
 #forward-button:hover:active:not(:-moz-lwtheme) {
   background-image: none;
   box-shadow: none;

--- a/browser/themes/shared/devedition.inc.css
+++ b/browser/themes/shared/devedition.inc.css
@@ -223,16 +223,22 @@ window:not([chromehidden~="toolbar"]) #u
   padding-bottom: 0;
 }
 
 /* Use smaller back button icon */
 #back-button {
   -moz-image-region: rect(0, 54px, 18px, 36px);
 }
 
+@media (min-resolution: 1.1dppx) {
+  #back-button {
+    -moz-image-region: rect(0, 108px, 36px, 72px);
+  }
+}
+
 .tab-background {
   visibility: hidden;
 }
 
 /* Tab separators */
 .tabbrowser-tab::after,
 .tabbrowser-tab::before {
   background: currentColor;

--- a/browser/themes/windows/devedition.css
+++ b/browser/themes/windows/devedition.css
@@ -38,48 +38,38 @@
 #TabsToolbar::after {
   display: none;
 }
 
 #back-button > .toolbarbutton-icon,
 #forward-button > .toolbarbutton-icon {
   background: var(--chrome-nav-buttons-background) !important;
   border-radius: 0 !important;
-  width: auto !important;
   height: auto !important;
   padding: var(--toolbarbutton-vertical-inner-padding) 5px !important;
   margin: 0 !important;
   border: 1px solid var(--chrome-nav-bar-controls-border-color) !important;
   box-shadow: none !important;
 }
 
+#back-button > .toolbarbutton-icon {
+  /* 18px icon + 2 * 5px padding + 2 * 1px border */
+  width: 30px !important;
+}
+
+#forward-button > .toolbarbutton-icon {
+  /* 18px icon + 2 * 5px padding + 1 * 1px border */
+  width: 29px !important;
+}
+
 /* the normal theme adds box-shadow: <stuff> !important when the back-button is [open]. Fix: */
 #back-button[open="true"] > .toolbarbutton-icon {
   box-shadow: none !important;
 }
 
-/* Force 1x image for back/forward button for now, otherwise it breaks the
-   layout - Bug 1165360. */
-@media (min-resolution: 1.1dppx) {
-  #back-button,
-  #forward-button {
-    list-style-image: url("chrome://browser/skin/Toolbar.png");
-  }
-
-  toolbar[brighttext] #back-button,
-  toolbar[brighttext] #forward-button {
-    list-style-image: url("chrome://browser/skin/Toolbar-inverted.png");
-  }
-
-  /* The back button region is already set in devedition.inc.css */
-  #forward-button {
-    -moz-image-region: rect(0px, 72px, 18px, 54px);
-  }
-}
-
 #forward-button > .toolbarbutton-icon {
   border-inline-start: none !important;
 }
 
 /* Override a box shadow for disabled back button */
 #main-window:not([customizing]) #back-button[disabled] > .toolbarbutton-icon {
   box-shadow: none !important;
 }