diff --git a/content/base/src/nsGkAtomList.h b/content/base/src/nsGkAtomList.h
index 47be89d54e51..0cea77e05bf4 100644
--- a/content/base/src/nsGkAtomList.h
+++ b/content/base/src/nsGkAtomList.h
@@ -2054,7 +2054,7 @@ GK_ATOM(az, "az")
 GK_ATOM(ba, "ba")
 GK_ATOM(crh, "crh")
 GK_ATOM(el, "el")
-GK_ATOM(ga_ie, "ga-ie")
+GK_ATOM(ga, "ga")
 GK_ATOM(nl, "nl")
 
 // Names for editor transactions
diff --git a/layout/generic/nsTextRunTransformations.cpp b/layout/generic/nsTextRunTransformations.cpp
index 03ddac7bef07..95feb300d962 100644
--- a/layout/generic/nsTextRunTransformations.cpp
+++ b/layout/generic/nsTextRunTransformations.cpp
@@ -235,6 +235,9 @@ enum LanguageSpecificCasingBehavior {
 static LanguageSpecificCasingBehavior
 GetCasingFor(const nsIAtom* aLang)
 {
+  if (!aLang) {
+      return eLSCB_None;
+  }
   if (aLang == nsGkAtoms::tr ||
       aLang == nsGkAtoms::az ||
       aLang == nsGkAtoms::ba ||
@@ -248,9 +251,19 @@ GetCasingFor(const nsIAtom* aLang)
   if (aLang == nsGkAtoms::el) {
     return eLSCB_Greek;
   }
-  if (aLang == nsGkAtoms::ga_ie) {
+  if (aLang == nsGkAtoms::ga) {
     return eLSCB_Irish;
   }
+
+  // Is there a region subtag we should ignore?
+  nsAtomString langStr(const_cast<nsIAtom*>(aLang));
+  int index = langStr.FindChar('-');
+  if (index > 0) {
+    langStr.Truncate(index);
+    nsCOMPtr<nsIAtom> truncatedLang = do_GetAtom(langStr);
+    return GetCasingFor(truncatedLang);
+  }
+
   return eLSCB_None;
 }