diff --git a/src/Umbraco.Core/Constants-SystemDirectories.cs b/src/Umbraco.Core/Constants-SystemDirectories.cs
index bf34aab989..40b0267d73 100644
--- a/src/Umbraco.Core/Constants-SystemDirectories.cs
+++ b/src/Umbraco.Core/Constants-SystemDirectories.cs
@@ -1,3 +1,5 @@
+using System;
+
 namespace Umbraco.Cms.Core
 {
     public static partial class Constants
@@ -42,7 +44,11 @@ namespace Umbraco.Cms.Core
             public const string Install = "~/install";
 
             public const string AppPlugins = "/App_Plugins";
-            public static string AppPluginIcons => "/Backoffice/Icons";
+
+            [Obsolete("Use PluginIcons instead")]
+            public const string AppPluginIcons = "/Backoffice/Icons";
+            public const string PluginIcons = "/backoffice/icons";
+            
             public const string CreatedPackages = "/created-packages";
 
 
diff --git a/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs b/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
index c79cbf9d94..fa448bdc86 100644
--- a/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
+++ b/src/Umbraco.Infrastructure/DependencyInjection/UmbracoBuilder.Services.cs
@@ -122,7 +122,8 @@ namespace Umbraco.Cms.Infrastructure.DependencyInjection
             var pluginLangFolders = appPlugins.Exists == false
                 ? Enumerable.Empty<LocalizedTextServiceSupplementaryFileSource>()
                 : appPlugins.GetDirectories()
-                    .SelectMany(x => x.GetDirectories("Lang", SearchOption.AllDirectories))
+                    // Check for both Lang & lang to support case sensitive file systems.
+                    .SelectMany(x => x.GetDirectories("?ang", SearchOption.AllDirectories).Where(x => x.Name.InvariantEquals("lang")))
                     .SelectMany(x => x.GetFiles("*.xml", SearchOption.TopDirectoryOnly))
                     .Select(x => new LocalizedTextServiceSupplementaryFileSource(x, false));
 
diff --git a/src/Umbraco.Web.BackOffice/Services/IconService.cs b/src/Umbraco.Web.BackOffice/Services/IconService.cs
index a1d634f41b..f1ab9ffb0e 100644
--- a/src/Umbraco.Web.BackOffice/Services/IconService.cs
+++ b/src/Umbraco.Web.BackOffice/Services/IconService.cs
@@ -104,8 +104,18 @@ namespace Umbraco.Cms.Web.BackOffice.Services
                 // iterate sub directories of app plugins
                 foreach (var dir in appPlugins.EnumerateDirectories())
                 {
-                    var iconPath = _hostingEnvironment.MapPathContentRoot($"{Constants.SystemDirectories.AppPlugins}/{dir.Name}{Constants.SystemDirectories.AppPluginIcons}");
-                    if (Directory.Exists(iconPath))
+                    // AppPluginIcons path was previoulsy the wrong case, so we first check for the prefered directory 
+                    // and then check the legacy directory.
+                    var iconPath = _hostingEnvironment.MapPathContentRoot($"{Constants.SystemDirectories.AppPlugins}/{dir.Name}{Constants.SystemDirectories.PluginIcons}");
+                    var iconPathExists = Directory.Exists(iconPath);
+
+                    if (!iconPathExists)
+                    {
+                        iconPath = _hostingEnvironment.MapPathContentRoot($"{Constants.SystemDirectories.AppPlugins}/{dir.Name}{Constants.SystemDirectories.AppPluginIcons}");
+                        iconPathExists = Directory.Exists(iconPath);
+                    }
+
+                    if (iconPathExists)
                     {
                         var dirIcons = new DirectoryInfo(iconPath).EnumerateFiles("*.svg", SearchOption.TopDirectoryOnly);
                         icons.UnionWith(dirIcons);