diff --git a/browser/themes/linux/browser.css b/browser/themes/linux/browser.css
index 7f1c78c38f5..3eaaad32f9e 100644
--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -1136,10 +1136,10 @@ toolbarbutton[constrain-size="true"][cui-areatype="toolbar"] > .toolbarbutton-ba
 
 %include ../shared/notification-icons.inc.css
 
-.popup-notification-description[popupid="addon-progress"],
-.popup-notification-description[popupid="addon-install-confirmation"] {
-  width: 27em;
-  max-width: 27em;
+.popup-notification-body[popupid="addon-progress"],
+.popup-notification-body[popupid="addon-install-confirmation"] {
+  width: 28em;
+  max-width: 28em;
 }
 
 .addon-install-confirmation-name {
diff --git a/browser/themes/osx/browser.css b/browser/themes/osx/browser.css
index f9374c1d5d4..43beabb6e0f 100644
--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -3687,10 +3687,10 @@ notification[value="loop-sharing-notification"] .messageImage {
   }
 }
 
-.popup-notification-description[popupid="addon-progress"],
-.popup-notification-description[popupid="addon-install-confirmation"] {
-  width: 27em;
-  max-width: 27em;
+.popup-notification-body[popupid="addon-progress"],
+.popup-notification-body[popupid="addon-install-confirmation"] {
+  width: 28em;
+  max-width: 28em;
 }
 
 #addon-progress-notification-progresstext,
diff --git a/browser/themes/windows/browser.css b/browser/themes/windows/browser.css
index b9ab4250e5f..63ff6fb0df5 100644
--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -2153,10 +2153,10 @@ toolbarbutton.bookmark-item[dragover="true"][open="true"] {
 
 %include ../shared/notification-icons.inc.css
 
-.popup-notification-description[popupid="addon-progress"],
-.popup-notification-description[popupid="addon-install-confirmation"] {
-  width: 27em;
-  max-width: 27em;
+.popup-notification-body[popupid="addon-progress"],
+.popup-notification-body[popupid="addon-install-confirmation"] {
+  width: 28em;
+  max-width: 28em;
 }
 
 .addon-install-confirmation-name {
diff --git a/toolkit/content/widgets/notification.xml b/toolkit/content/widgets/notification.xml
index 028a6681342..d2cb07916d6 100644
--- a/toolkit/content/widgets/notification.xml
+++ b/toolkit/content/widgets/notification.xml
@@ -475,7 +475,7 @@
         <xul:image class="popup-notification-icon"
                    xbl:inherits="popupid,src=icon"/>
       </xul:vbox>
-      <xul:vbox>
+      <xul:vbox class="popup-notification-body" xbl:inherits="popupid">
         <xul:hbox align="start">
           <xul:vbox flex="1">
             <xul:label class="popup-notification-origin header"
diff --git a/toolkit/themes/linux/global/notification.css b/toolkit/themes/linux/global/notification.css
index a2e29a33dc7..f8f70044f9a 100644
--- a/toolkit/themes/linux/global/notification.css
+++ b/toolkit/themes/linux/global/notification.css
@@ -63,8 +63,8 @@ notification[type="critical"] {
 
 /* Popup notification */
 
-.popup-notification-description {
-  max-width: 24em;
+.popup-notification-body {
+  max-width: 25em;
 }
 
 .popup-notification-origin:not([value]),
diff --git a/toolkit/themes/osx/global/notification.css b/toolkit/themes/osx/global/notification.css
index 9660ec0eaa9..99f2b82116d 100644
--- a/toolkit/themes/osx/global/notification.css
+++ b/toolkit/themes/osx/global/notification.css
@@ -101,8 +101,8 @@ notification[type="info"]:not([value="translation"]) .close-icon:not(:hover) {
 
 /* Popup notification */
 
-.popup-notification-description {
-  max-width: 24em;
+.popup-notification-body {
+  max-width: 25em;
 }
 
 .popup-notification-origin:not([value]),
diff --git a/toolkit/themes/windows/global/notification.css b/toolkit/themes/windows/global/notification.css
index f2bafd58fef..4e2c144b5db 100644
--- a/toolkit/themes/windows/global/notification.css
+++ b/toolkit/themes/windows/global/notification.css
@@ -58,8 +58,8 @@ notification[type="critical"] {
 
 /* Popup notification */
 
-.popup-notification-description {
-  max-width: 24em;
+.popup-notification-body {
+  max-width: 25em;
 }
 
 .popup-notification-origin:not([value]),