diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 88ef30be4..6b1196054 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -6,6 +6,8 @@
 * New: Support for unicode characters in type names. This simplifies using an
   [ubiquitous language](http://www.jamesshore.com/Agile-Book/ubiquitous_language.html)
   in non-english domains
+* Fixed: Include hyphen in prefix validation for identity values. This fixes a bug
+  where invalid identities could be created (e.g. `ThingyId.With("thingyINVALID-a41e...")`)
 
 ### New in 0.51.3155 (released 2017-10-25)
 
diff --git a/Source/EventFlow.Tests/UnitTests/Core/IdentityTests.cs b/Source/EventFlow.Tests/UnitTests/Core/IdentityTests.cs
index 1127a29b7..014aae993 100644
--- a/Source/EventFlow.Tests/UnitTests/Core/IdentityTests.cs
+++ b/Source/EventFlow.Tests/UnitTests/Core/IdentityTests.cs
@@ -118,6 +118,7 @@ public void NewDeterministic_IsValid()
         }
 
         [TestCase("da7ab6b1-c513-581f-a1a0-7cdf17109deb")]
+        [TestCase("thingyid-da7ab6b1-c513-581f-a1a0-7cdf17109deb")]
         [TestCase("thingy-769077C6-F84D-46E3-AD2E-828A576AAAF3")]
         [TestCase("thingy-pppppppp-pppp-pppp-pppp-pppppppppppp")]
         [TestCase("funny-da7ab6b1-c513-581f-a1a0-7cdf17109deb")]
diff --git a/Source/EventFlow/Core/Identity.cs b/Source/EventFlow/Core/Identity.cs
index 70ad7aa22..eb5a28b0c 100644
--- a/Source/EventFlow/Core/Identity.cs
+++ b/Source/EventFlow/Core/Identity.cs
@@ -35,16 +35,16 @@ public abstract class Identity<T> : SingleValueObject<string>, IIdentity
         where T : Identity<T>
     {
         // ReSharper disable StaticMemberInGenericType
-        private static readonly string Name;
+        private static readonly string NameWithDash;
         private static readonly Regex ValueValidation;
         // ReSharper enable StaticMemberInGenericType
 
         static Identity()
         {
             var nameReplace = new Regex("Id$");
-            Name = nameReplace.Replace(typeof(T).Name, string.Empty).ToLowerInvariant();
+            NameWithDash = nameReplace.Replace(typeof(T).Name, string.Empty).ToLowerInvariant() + "-";
             ValueValidation = new Regex(
-                @"^[\p{Ll}\p{Lm}\p{Lo}\p{Nd}]+\-(?<guid>[a-f0-9]{8}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{12})$",
+                @"^[^\-]+\-(?<guid>[a-f0-9]{8}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{12})$",
                 RegexOptions.Compiled);
         }
 
@@ -86,7 +86,7 @@ public static T With(string value)
 
         public static T With(Guid guid)
         {
-            var value = $"{Name}-{guid:D}";
+            var value = $"{NameWithDash}{guid:D}";
             return With(value);
         }
 
@@ -105,8 +105,8 @@ public static IEnumerable<string> Validate(string value)
 
             if (!string.Equals(value.Trim(), value, StringComparison.OrdinalIgnoreCase))
                 yield return $"Identity '{value}' of type '{typeof(T).PrettyPrint()}' contains leading and/or traling spaces";
-            if (!value.StartsWith(Name))
-                yield return $"Identity '{value}' of type '{typeof(T).PrettyPrint()}' does not start with '{Name}'";
+            if (!value.StartsWith(NameWithDash))
+                yield return $"Identity '{value}' of type '{typeof(T).PrettyPrint()}' does not start with '{NameWithDash}'";
             if (!ValueValidation.IsMatch(value))
                 yield return $"Identity '{value}' of type '{typeof(T).PrettyPrint()}' does not follow the syntax '[NAME]-[GUID]' in lower case";
         }