diff --git a/toolkit/components/prompts/content/commonDialog.xul b/toolkit/components/prompts/content/commonDialog.xul
index 65b8bb49deea..cd9a81e050b4 100644
--- a/toolkit/components/prompts/content/commonDialog.xul
+++ b/toolkit/components/prompts/content/commonDialog.xul
@@ -61,7 +61,7 @@
     <rows>
       <row>
         <hbox id="iconContainer" align="start">
-          <image id="infoIcon" class="spaced"/>
+          <image id="infoIcon"/>
         </hbox>
         <vbox id="infoContainer"
 #ifndef XP_MACOSX
diff --git a/toolkit/components/prompts/test/prompt_common.js b/toolkit/components/prompts/test/prompt_common.js
index 43230af0b694..6b90383468fd 100644
--- a/toolkit/components/prompts/test/prompt_common.js
+++ b/toolkit/components/prompts/test/prompt_common.js
@@ -49,7 +49,7 @@ function checkPromptState(promptState, expectedState) {
     is(promptState.checkMsg, expectedState.checkMsg, "Checking checkbox label");
     is(promptState.checked, expectedState.checked, "Checking checkbox checked");
     if (!isTabModal)
-      is(promptState.iconClass, "spaced " + expectedState.iconClass, "Checking expected icon CSS class");
+      is(promptState.iconClass, expectedState.iconClass, "Checking expected icon CSS class");
     is(promptState.textValue, expectedState.textValue, "Checking textbox value");
     is(promptState.passValue, expectedState.passValue, "Checking passbox value");
 
diff --git a/toolkit/themes/linux/global/commonDialog.css b/toolkit/themes/linux/global/commonDialog.css
index d556dd31655e..7776d28a8ad1 100644
--- a/toolkit/themes/linux/global/commonDialog.css
+++ b/toolkit/themes/linux/global/commonDialog.css
@@ -16,7 +16,5 @@
 #infoIcon {
   max-width: 48px;
   max-height: 48px;
-  /* The 'spaced' class does this already. It's repeated here to make it clearer
-     what margin values the #iconContainer's min-height and max-height depend on: */
   margin: 3px 5px 4px;
 }
diff --git a/toolkit/themes/linux/global/global.css b/toolkit/themes/linux/global/global.css
index 86a44ec73967..49a596fe60e9 100644
--- a/toolkit/themes/linux/global/global.css
+++ b/toolkit/themes/linux/global/global.css
@@ -211,10 +211,6 @@ label[disabled="true"] {
   padding: 5px;
 }
 
-.spaced {
-  margin: 3px 5px 4px;
-}
-
 .text-link {
   color: -moz-nativehyperlinktext;
   cursor: pointer;
diff --git a/toolkit/themes/osx/global/commonDialog.css b/toolkit/themes/osx/global/commonDialog.css
index 1791133199c5..94a93e744acb 100644
--- a/toolkit/themes/osx/global/commonDialog.css
+++ b/toolkit/themes/osx/global/commonDialog.css
@@ -19,6 +19,7 @@
 }
 
 #infoIcon {
+  margin: 3px 5px 4px;
   margin-inline-end: 14px;
 }
 
diff --git a/toolkit/themes/osx/global/global.css b/toolkit/themes/osx/global/global.css
index 185068cfb990..8087b001deb4 100644
--- a/toolkit/themes/osx/global/global.css
+++ b/toolkit/themes/osx/global/global.css
@@ -172,10 +172,6 @@ label[disabled="true"] {
   padding: 5px;
 }
 
-.spaced {
-  margin: 3px 5px 4px;
-}
-
 .text-link {
   color: -moz-nativehyperlinktext;
   cursor: pointer;
diff --git a/toolkit/themes/windows/global/commonDialog.css b/toolkit/themes/windows/global/commonDialog.css
index 3a1b9f43de5a..533134de9146 100644
--- a/toolkit/themes/windows/global/commonDialog.css
+++ b/toolkit/themes/windows/global/commonDialog.css
@@ -6,3 +6,7 @@
   margin-inline-start: -8px;
   margin-inline-end: -10px;
 }
+
+#infoIcon {
+  margin: 3px 5px 4px;
+}
diff --git a/toolkit/themes/windows/global/global.css b/toolkit/themes/windows/global/global.css
index 92990a7fa4de..47381edb1d6b 100644
--- a/toolkit/themes/windows/global/global.css
+++ b/toolkit/themes/windows/global/global.css
@@ -220,10 +220,6 @@ label[disabled="true"] {
   padding: 5px;
 }
 
-.spaced {
-  margin: 3px 5px 4px;
-}
-
 .text-link {
   color: -moz-nativehyperlinktext;
   cursor: pointer;