diff --git a/SteamStorefrontAPI/Endpoints/AppDetails.cs b/SteamStorefrontAPI/Endpoints/AppDetails.cs
index 881c5a4..fb3bbab 100644
--- a/SteamStorefrontAPI/Endpoints/AppDetails.cs
+++ b/SteamStorefrontAPI/Endpoints/AppDetails.cs
@@ -40,7 +40,7 @@ namespace SteamStorefrontAPI
         {
             string steamUri = $"{steamBaseUri}?appids={AppId}";
             steamUri = string.IsNullOrWhiteSpace(CountryCode) ? steamUri : $"{steamUri}&cc={CountryCode}";
-            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language}";
+            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language.ToLower()}";
 
             var response = await client.GetAsync(steamUri);
             if (!response.IsSuccessStatusCode) { return null; }
diff --git a/SteamStorefrontAPI/Endpoints/Featured.cs b/SteamStorefrontAPI/Endpoints/Featured.cs
index 352bbe9..8d355bf 100644
--- a/SteamStorefrontAPI/Endpoints/Featured.cs
+++ b/SteamStorefrontAPI/Endpoints/Featured.cs
@@ -39,7 +39,7 @@ namespace SteamStorefrontAPI
         {
             string steamUri = steamBaseUri;
             steamUri = string.IsNullOrWhiteSpace(CountryCode) ? steamUri : $"{steamUri}&cc={CountryCode}";
-            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language}";
+            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language.ToLower()}";
 
             var response = await client.GetAsync(steamUri);
             if (!response.IsSuccessStatusCode) { return null; }
diff --git a/SteamStorefrontAPI/Endpoints/FeaturedCategories.cs b/SteamStorefrontAPI/Endpoints/FeaturedCategories.cs
index 5aa1ed8..c9ae61f 100644
--- a/SteamStorefrontAPI/Endpoints/FeaturedCategories.cs
+++ b/SteamStorefrontAPI/Endpoints/FeaturedCategories.cs
@@ -39,7 +39,7 @@ namespace SteamStorefrontAPI
         {
             string steamUri = steamBaseUri;
             steamUri = string.IsNullOrWhiteSpace(CountryCode) ? steamUri : $"{steamUri}&cc={CountryCode}";
-            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language}";
+            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language.ToLower()}";
 
             var response = await client.GetAsync(steamUri);
             if (!response.IsSuccessStatusCode) { return null; }
diff --git a/SteamStorefrontAPI/Endpoints/PackageDetails.cs b/SteamStorefrontAPI/Endpoints/PackageDetails.cs
index 37a3db5..16cd08b 100644
--- a/SteamStorefrontAPI/Endpoints/PackageDetails.cs
+++ b/SteamStorefrontAPI/Endpoints/PackageDetails.cs
@@ -42,7 +42,7 @@ namespace SteamStorefrontAPI
         {
             string steamUri = $"{steamBaseUri}?packageids={PackageId}";
             steamUri = string.IsNullOrWhiteSpace(CountryCode) ? steamUri : $"{steamUri}&cc={CountryCode}";
-            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language}";
+            steamUri = string.IsNullOrWhiteSpace(Language) ? steamUri : $"{steamUri}&l={Language.ToLower()}";
 
             var response = await client.GetAsync(steamUri);
             if (!response.IsSuccessStatusCode) { return null; }