diff --git a/Readme.md b/Readme.md
index 97c093d..6ef9c9f 100644
--- a/Readme.md
+++ b/Readme.md
@@ -21,7 +21,7 @@ This library add support for the following types:
 Implementation based on this [UUID RFC Draft](https://datatracker.ietf.org/doc/html/draft-ietf-uuidrev-rfc4122bis-03)
 
 In addition to UUID, there is also support for [TypeIDs](https://github.com/jetpack-io/typeid). TypeIDs are a modern, 
-type-safe extension of UUIDv7 
+type-safe extension of UUIDv7. This implementation is compatible with the [0.3.0 version of the specification](https://github.com/jetify-com/typeid/tree/main/spec#typeid-specification-version-030)
 
 ##  Quickstart
 
diff --git a/core/src/main/scala/tech/ant8e/uuid4cats/TypeID.scala b/core/src/main/scala/tech/ant8e/uuid4cats/TypeID.scala
index 496922f..acf2ac9 100644
--- a/core/src/main/scala/tech/ant8e/uuid4cats/TypeID.scala
+++ b/core/src/main/scala/tech/ant8e/uuid4cats/TypeID.scala
@@ -110,8 +110,7 @@ object TypeID {
       enforceUUIDV7: Boolean = true
   ): ValidatedNec[DecodeError, TypeID] = {
     val re =
-      "^([a-z]{0,63})(_?)([0123456789abcdefghjkmnpqrstvwxyz]+)$".r
-
+      "^([a-z](?:[a-z_]{0,61}[a-z])?)?(_)?([0123456789abcdefghjkmnpqrstvwxyz]{26})$".r
     def parseID(id: String): Validated[DecodeError, UUID] =
       UUIDBase32
         .fromBase32(id)
@@ -124,7 +123,7 @@ object TypeID {
         }
 
     typeIDString match {
-      case re(prefix, sep, id) =>
+      case re(prefix, sep, id) if prefix != null && sep != null =>
         (
           Validated
             .cond(
@@ -135,6 +134,8 @@ object TypeID {
             .toValidatedNec,
           parseID(id).toValidatedNec
         ).mapN { case (prefix_, uuid_) => newTypeID(prefix_, uuid_) }
+      case re(null, null, id) =>
+        parseID(id).toValidatedNec.map(uuid => newTypeID("", uuid))
       case _ => Validated.invalidNec(NotParseableTypeID)
     }
 
@@ -207,7 +208,7 @@ object TypeID {
       prefix: String
   ): Validated[BuildError, String] = Option(prefix)
     .map(prefix_ => {
-      if ("[a-z]{0,63}".r.matches(prefix_))
+      if ("^([a-z]([a-z_]{0,61}[a-z])?)?$".r.matches(prefix_))
         Validated.Valid(prefix_)
       else Validated.Invalid(InvalidPrefix)
     })
diff --git a/core/src/test/scala/tech/ant8e/uuid4cats/TypeIDSuite.scala b/core/src/test/scala/tech/ant8e/uuid4cats/TypeIDSuite.scala
index b690820..2b750d4 100644
--- a/core/src/test/scala/tech/ant8e/uuid4cats/TypeIDSuite.scala
+++ b/core/src/test/scala/tech/ant8e/uuid4cats/TypeIDSuite.scala
@@ -82,7 +82,15 @@ class TypeIDSuite extends FunSuite {
       prefix = "prefix",
       uuid = uuid"01890a5d-ac96-774b-bcce-b302099a8057"
     )
+
+    // prefix-underscore added in v0.3.0
+    assertValidEncoding(
+      typeID = "pre_fix_00000000000000000000000000",
+      prefix = "pre_fix",
+      uuid = uuid"00000000-0000-0000-0000-000000000000"
+    )
   }
+
   test("TypeID should not  build invalid typeIDs") {
     val tooLongPrefix =
       "0123456789012345678901234567890123456789012345678901234567890123456789"
@@ -167,9 +175,6 @@ class TypeIDSuite extends FunSuite {
     // prefix-period
     assertInvalidDecoding(typeID = "pre.fix_00000000000000000000000000")
 
-    // prefix-underscore
-    assertInvalidDecoding(typeID = "pre_fix_00000000000000000000000000")
-
     // prefix-non-ascii
     assertInvalidDecoding(typeID = "préfix_00000000000000000000000000")
 
@@ -224,6 +229,17 @@ class TypeIDSuite extends FunSuite {
     assertInvalidDecoding(
       typeID = "prefix0000000000000000000000000g"
     )
+
+    // prefix-underscore-start
+    assertInvalidDecoding(
+      typeID = "_prefix_00000000000000000000000000"
+    )
+
+    // prefix-underscore-end
+    assertInvalidDecoding(
+      typeID = "prefix__00000000000000000000000000"
+    )
+
   }
 
   test("TypeID should have an Eq instance") {