diff --git a/gfx/src/thebes/nsThebesFontEnumerator.cpp b/gfx/src/thebes/nsThebesFontEnumerator.cpp
index 2b4c4083e52..d1e5f817d97 100644
--- a/gfx/src/thebes/nsThebesFontEnumerator.cpp
+++ b/gfx/src/thebes/nsThebesFontEnumerator.cpp
@@ -74,7 +74,14 @@ nsThebesFontEnumerator::EnumerateFonts(const char *aLangGroup,
     else
         generic.SetIsVoid(PR_TRUE);
 
-    nsCOMPtr<nsIAtom> langGroupAtom = do_GetAtom(aLangGroup);
+    nsCOMPtr<nsIAtom> langGroupAtom;
+    if (aLangGroup) {
+        nsCAutoString lowered;
+        lowered.Assign(aLangGroup);
+        ToLowerCase(lowered);
+        langGroupAtom = do_GetAtom(lowered);
+    }
+
     nsresult rv = gfxPlatform::GetPlatform()->GetFontList(langGroupAtom, generic, fontList);
 
     if (NS_FAILED(rv)) {
diff --git a/gfx/thebes/src/gfxFontconfigUtils.cpp b/gfx/thebes/src/gfxFontconfigUtils.cpp
index d7635fbb371..1428ece4fb7 100644
--- a/gfx/thebes/src/gfxFontconfigUtils.cpp
+++ b/gfx/thebes/src/gfxFontconfigUtils.cpp
@@ -282,8 +282,10 @@ gfxFontconfigUtils::GetFontList(nsIAtom *aLangGroup,
     aListOfFonts.Clear();
 
     nsTArray<nsCString> fonts;
-    nsCString langGroupStr;
-    aLangGroup->ToUTF8String(langGroupStr);
+    nsCAutoString langGroupStr;
+    if (aLangGroup) {
+        aLangGroup->ToUTF8String(langGroupStr);
+    }
     nsresult rv = GetFontListInternal(fonts, langGroupStr);
     if (NS_FAILED(rv))
         return rv;
diff --git a/gfx/thebes/src/gfxOS2Platform.cpp b/gfx/thebes/src/gfxOS2Platform.cpp
index b027de78915..982c03d5a36 100644
--- a/gfx/thebes/src/gfxOS2Platform.cpp
+++ b/gfx/thebes/src/gfxOS2Platform.cpp
@@ -115,8 +115,10 @@ gfxOS2Platform::GetFontList(nsIAtom *aLangGroup,
                             nsTArray<nsString>& aListOfFonts)
 {
 #ifdef DEBUG_thebes
-    const char *langgroup;
-    aLangGroup->GetUTF8String(&langgroup);
+    const char *langgroup = "(null)";
+    if (aLangGroup) {
+        aLangGroup->GetUTF8String(&langgroup);
+    }
     char *family = ToNewCString(aGenericFamily);
     printf("gfxOS2Platform::GetFontList(%s, %s, ..)\n",
            langgroup, family);