diff --git a/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs b/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
index 2803b942ad..76ee2b7aad 100644
--- a/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
+++ b/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
@@ -95,7 +95,7 @@ namespace Avalonia.Media.Fonts
         {
             if (!Source.IsAbsoluteUri && BaseUri != null)
             {
-                return string.Empty + BaseUri + Source;
+                return BaseUri.Authority + Source;
             }
 
             return Source.ToString();
diff --git a/src/Avalonia.Visuals/Media/Fonts/FontFamilyLoader.cs b/src/Avalonia.Visuals/Media/Fonts/FontFamilyLoader.cs
index 623125164c..1e1049d017 100644
--- a/src/Avalonia.Visuals/Media/Fonts/FontFamilyLoader.cs
+++ b/src/Avalonia.Visuals/Media/Fonts/FontFamilyLoader.cs
@@ -19,8 +19,10 @@ namespace Avalonia.Media.Fonts
 
         public static IEnumerable<Uri> LoadFontAssets(FontFamilyKey fontFamilyKey)
         {
-            if (fontFamilyKey.Source.OriginalString.Contains(".ttf")
-                || fontFamilyKey.Source.OriginalString.Contains(".otf"))
+            var sourceWithoutArguments = fontFamilyKey.Source.OriginalString.Split('?').First();
+
+            if (sourceWithoutArguments.EndsWith(".ttf")
+                || sourceWithoutArguments.EndsWith(".otf"))
             {
                 return GetFontAssetsByExpression(fontFamilyKey);
             }