diff --git a/src/Context.php b/src/Context.php
index 7e05016..3de3d80 100644
--- a/src/Context.php
+++ b/src/Context.php
@@ -68,7 +68,7 @@ public function __construct() {
 
     public function setRegistration($value) {
         if (isset($value) && ! preg_match(Util::UUID_REGEX, $value)) {
-            throw new InvalidArgumentException('arg1 must be a UUIDv4');
+            throw new InvalidArgumentException('arg1 must be a UUID');
         }
         $this->registration = $value;
         return $this;
diff --git a/src/State.php b/src/State.php
index 4b6ad63..93b805b 100644
--- a/src/State.php
+++ b/src/State.php
@@ -52,7 +52,7 @@ public function getAgent() { return $this->agent; }
 
     public function setRegistration($value) {
         if (isset($value) && ! preg_match(Util::UUID_REGEX, $value)) {
-            throw new InvalidArgumentException('arg1 must be a UUIDv4');
+            throw new InvalidArgumentException('arg1 must be a UUID');
         }
 
         $this->registration = $value;
diff --git a/src/Statement.php b/src/Statement.php
index c730f60..0e227be 100644
--- a/src/Statement.php
+++ b/src/Statement.php
@@ -89,7 +89,7 @@ public function stamp() {
 
     public function setId($value) {
         if (isset($value) && ! preg_match(Util::UUID_REGEX, $value)) {
-            throw new InvalidArgumentException('arg1 must be a UUIDv4');
+            throw new InvalidArgumentException('arg1 must be a UUID');
         }
         $this->id = $value;
         return $this;
diff --git a/src/StatementRef.php b/src/StatementRef.php
index 0f4a147..dd25446 100644
--- a/src/StatementRef.php
+++ b/src/StatementRef.php
@@ -42,7 +42,7 @@ public function getObjectType() { return $this->objectType; }
 
     public function setId($value) {
         if (isset($value) && ! preg_match(Util::UUID_REGEX, $value)) {
-            throw new InvalidArgumentException('arg1 must be a UUIDv4');
+            throw new InvalidArgumentException('arg1 must be a UUID');
         }
         $this->id = $value;
         return $this;
diff --git a/src/Util.php b/src/Util.php
index 0a533cf..a8c6c0a 100644
--- a/src/Util.php
+++ b/src/Util.php
@@ -19,7 +19,7 @@
 
 class Util
 {
-    const UUID_REGEX = '/[a-f0-9]{8}-[a-f0-9]{4}-4[a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}/';
+    const UUID_REGEX = '/[a-f0-9]{8}-[a-f0-9]{4}-[1-5][a-f0-9]{3}-[89ab][a-f0-9]{3}-[a-f0-9]{12}/i';
 
     //
     // Based on code from