--- a/gfx/thebes/gfxMacPlatformFontList.h
+++ b/gfx/thebes/gfxMacPlatformFontList.h
@@ -159,16 +159,17 @@ class gfxMacPlatformFontList : public gf
   virtual ~gfxMacPlatformFontList();
 
   // initialize font lists
   nsresult InitFontListForPlatform() override;
   void InitSharedFontListForPlatform() override;
 
   // special case font faces treated as font families (set via prefs)
   void InitSingleFaceList();
+  void InitAliasesForSingleFaceList();
 
   // initialize system fonts
   void InitSystemFontNames();
 
   // helper function to lookup in both hidden system fonts and normal fonts
   gfxFontFamily* FindSystemFontFamily(const nsACString& aFamily);
 
   static void RegisteredFontsChangedNotificationCallback(

--- a/gfx/thebes/gfxMacPlatformFontList.mm
+++ b/gfx/thebes/gfxMacPlatformFontList.mm
@@ -1005,20 +1005,85 @@ void gfxMacPlatformFontList::InitSharedF
       GenerateFontListKey(name, key);
       bool isHidden = key.EqualsLiteral("lastresort") || key[0] == '.';
       families.AppendElement(fontlist::Family::InitData(key, name, 0, isHidden));
     }
     CFRelease(familyNames);
     ApplyWhitelist(families);
     families.Sort();
     SharedFontList()->SetFamilyNames(families);
+    InitAliasesForSingleFaceList();
     GetPrefsAndStartLoader();
   }
 }
 
+void gfxMacPlatformFontList::InitAliasesForSingleFaceList() {
+  AutoTArray<nsCString, 10> singleFaceFonts;
+  gfxFontUtils::GetPrefsFontList("font.single-face-list", singleFaceFonts);
+
+  for (auto& familyName : singleFaceFonts) {
+    LOG_FONTLIST(("(fontlist-singleface) face name: %s\n", familyName.get()));
+    // Each entry in the "single face families" list is expected to be a
+    // colon-separated pair of FaceName:Family,
+    // where FaceName is the individual face name (psname) of a font
+    // that should be exposed as a separate family name,
+    // and Family is the standard family to which that face belongs.
+    // The only such face listed by default is
+    //    Osaka-Mono:Osaka
+    auto colon = familyName.FindChar(':');
+    if (colon == kNotFound) {
+      continue;
+    }
+
+    // Look for the parent family in the main font family list,
+    // and ensure we have loaded its list of available faces.
+    nsAutoCString key;
+    GenerateFontListKey(Substring(familyName, colon + 1), key);
+    fontlist::Family* family = SharedFontList()->FindFamily(key);
+    if (!family) {
+      // The parent family is not present, so just ignore this entry.
+      continue;
+    }
+    if (!family->IsInitialized()) {
+      if (!gfxPlatformFontList::InitializeFamily(family)) {
+        // This shouldn't ever fail, but if it does, we can safely ignore it.
+        MOZ_ASSERT(false, "failed to initialize font family");
+        continue;
+      }
+    }
+
+    // Truncate the entry from prefs at the colon, so now it is just the
+    // desired single-face-family name.
+    familyName.Truncate(colon);
+
+    // Look through the family's faces to see if this one is present.
+    fontlist::FontList* list = SharedFontList();
+    const fontlist::Pointer* facePtrs = family->Faces(list);
+    for (size_t i = 0; i < family->NumFaces(); i++) {
+      if (facePtrs[i].IsNull()) {
+        continue;
+      }
+      auto face = static_cast<const fontlist::Face*>(facePtrs[i].ToPtr(list));
+      if (face->mDescriptor.AsString(list).Equals(familyName)) {
+        // Found it! Create an entry in the Alias table.
+        GenerateFontListKey(familyName, key);
+        if (SharedFontList()->FindFamily(key) || mAliasTable.Get(familyName)) {
+          // If the family name is already known, something's misconfigured;
+          // just ignore it.
+          MOZ_ASSERT(false, "single-face family already known");
+          break;
+        }
+        auto af = mAliasTable.LookupOrAdd(familyName);
+        af->AppendElement(facePtrs[i]);
+        break;
+      }
+    }
+  }
+}
+
 void gfxMacPlatformFontList::InitSingleFaceList() {
   AutoTArray<nsCString, 10> singleFaceFonts;
   gfxFontUtils::GetPrefsFontList("font.single-face-list", singleFaceFonts);
 
   for (auto& familyName : singleFaceFonts) {
     LOG_FONTLIST(("(fontlist-singleface) face name: %s\n", familyName.get()));
     // Each entry in the "single face families" list is expected to be a
     // colon-separated pair of FaceName:Family,