diff --git a/src/Orchard.Web/Modules/Orchard.ContentTypes/Controllers/AdminController.cs b/src/Orchard.Web/Modules/Orchard.ContentTypes/Controllers/AdminController.cs
index 78ec18c63..df8589a95 100644
--- a/src/Orchard.Web/Modules/Orchard.ContentTypes/Controllers/AdminController.cs
+++ b/src/Orchard.Web/Modules/Orchard.ContentTypes/Controllers/AdminController.cs
@@ -53,12 +53,16 @@ namespace Orchard.ContentTypes.Controllers {
             if (String.IsNullOrWhiteSpace(viewModel.DisplayName)) {
                 ModelState.AddModelError("DisplayName", T("The Display Name name can't be empty.").ToString());
             }
-            
-            if ( _contentDefinitionService.GetTypes().Any(t => String.Equals(t.Name.Trim(), viewModel.Name.Trim(), StringComparison.OrdinalIgnoreCase)) ) {
+
+            if (_contentDefinitionService.GetTypes().Any(t => String.Equals(t.Name.Trim(), viewModel.Name.Trim(), StringComparison.OrdinalIgnoreCase))) {
                 ModelState.AddModelError("Name", T("A type with the same Id already exists.").ToString());
             }
 
-            if ( _contentDefinitionService.GetTypes().Any(t => String.Equals(t.DisplayName.Trim(), viewModel.DisplayName.Trim(), StringComparison.OrdinalIgnoreCase)) ) {
+            if (!String.IsNullOrWhiteSpace(viewModel.Name) && !ContentDefinitionService.IsLetter(viewModel.Name[0])) {
+                ModelState.AddModelError("Name", T("The technical name must start with a letter.").ToString());
+            }
+
+            if (_contentDefinitionService.GetTypes().Any(t => String.Equals(t.DisplayName.Trim(), viewModel.DisplayName.Trim(), StringComparison.OrdinalIgnoreCase))) {
                 ModelState.AddModelError("DisplayName", T("A type with the same Name already exists.").ToString());
             }
 
diff --git a/src/Orchard.Web/Modules/Orchard.ContentTypes/Services/ContentDefinitionService.cs b/src/Orchard.Web/Modules/Orchard.ContentTypes/Services/ContentDefinitionService.cs
index 5d4ab98ca..fe04b5f86 100644
--- a/src/Orchard.Web/Modules/Orchard.ContentTypes/Services/ContentDefinitionService.cs
+++ b/src/Orchard.Web/Modules/Orchard.ContentTypes/Services/ContentDefinitionService.cs
@@ -71,6 +71,11 @@ namespace Orchard.ContentTypes.Services {
             if(String.IsNullOrWhiteSpace(name)) {
                 name = GenerateContentTypeNameFromDisplayName(displayName);
             }
+            else {
+                if(!IsLetter(name[0])) {
+                    throw new ArgumentException("Content type name must start with a letter", "name");
+                }
+            }
 
             while ( _contentDefinitionManager.GetTypeDefinition(name) != null )
                 name = VersionName(name);
@@ -235,11 +240,23 @@ namespace Orchard.ContentTypes.Services {
             name = dissallowed.Replace(name, String.Empty);
             name = name.Trim();
 
+            // don't allow non A-Z chars as first letter, as they are not allowed in prefixes
+            if(name.Length > 0) {
+                if (!IsLetter(name[0])) {
+                    name = name.Substring(1);
+                }
+            }
+
             if (name.Length > 128)
                 name = name.Substring(0, 128);
+
             return name;
         }
 
+        public static bool IsLetter(char c) {
+            return ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z');
+        }
+
         //gratuitously stolen from the RoutableService
         public string GenerateContentTypeNameFromDisplayName(string displayName) {
             displayName = SafeName(displayName);