diff --git a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Commands/NewExtensionForm.cs b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Commands/NewExtensionForm.cs
index aca45f3494..14cd4a0e16 100644
--- a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Commands/NewExtensionForm.cs
+++ b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Commands/NewExtensionForm.cs
@@ -55,7 +55,7 @@ internal sealed partial class NewExtensionForm : NewExtensionFormBase
             "errorMessage": {{FormatJsonString(Properties.Resources.builtin_create_extension_name_required)}},
             "id": "ExtensionName",
             "placeholder": "ExtensionName",
-            "regex": "^[^\\s]+$"
+            "regex": "^[a-zA-Z_][a-zA-Z0-9_]*$"
         },
         {
             "type": "TextBlock",
diff --git a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs
index 5552304ca2..5c4d961aa7 100644
--- a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs
+++ b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs
@@ -178,7 +178,7 @@ namespace Microsoft.CmdPal.UI.ViewModels.Properties {
         }
         
         /// <summary>
-        ///   Looks up a localized string similar to Extension name is required, without spaces.
+        ///   Looks up a localized string similar to Extension name is required and must be a valid C# identifier (start with a letter or underscore, followed by letters, numbers, or underscores).
         /// </summary>
         public static string builtin_create_extension_name_required {
             get {
diff --git a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx
index 4dc5a1539f..a1755ab097 100644
--- a/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx
+++ b/src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx
@@ -195,7 +195,7 @@
     <value>Extension name</value>
   </data>
   <data name="builtin_create_extension_name_required" xml:space="preserve">
-    <value>Extension name is required, without spaces</value>
+    <value>Extension name is required and must be a valid C# identifier (start with a letter or underscore, followed by letters, numbers, or underscores)</value>
   </data>
   <data name="builtin_create_extension_display_name_header" xml:space="preserve">
     <value>Display name</value>