diff --git a/src/main/scala/authentikat/jwt/JwtHeader.scala b/src/main/scala/authentikat/jwt/JwtHeader.scala
index b57a9c8..7e65b1f 100644
--- a/src/main/scala/authentikat/jwt/JwtHeader.scala
+++ b/src/main/scala/authentikat/jwt/JwtHeader.scala
@@ -2,22 +2,27 @@ package authentikat.jwt
 
 import org.json4s._
 import org.json4s.jackson.JsonMethods._
-import org.json4s.jackson.Serialization
 
-import util.control.Exception.allCatch
+import scala.util.control.Exception.allCatch
 
-case class JwtHeader(algorithm: Option[String],
-    contentType: Option[String],
-    typ: Option[String]) {
+case class JwtHeader(
+                      algorithm: Option[String],
+                      contentType: Option[String],
+                      typ: Option[String]
+                    ) {
 
   def asJsonString: String = {
     val toSerialize =
-      algorithm.map(x ⇒ ("alg", x)).toSeq ++
-        contentType.map(x ⇒ ("cty", x)).toSeq ++
-        typ.map(x ⇒ ("typ", x)).toSeq
+      algorithm.map(x => ("alg" -> x)).toSeq ++
+        contentType.map(x => ("cty", x)).toSeq ++
+        typ.map(x => ("typ", x)).toSeq
 
+    val map = toSerialize.toMap
+
+    import org.json4s.native.Serialization.write
     implicit val formats = org.json4s.DefaultFormats
-    org.json4s.jackson.Serialization.write(toSerialize)
+
+    write(map)
   }
 }
 
@@ -27,7 +32,7 @@ object JwtHeader {
 
   implicit val formats = DefaultFormats
 
-  def apply(algorithm: String = null, contentType: String = null, typ: String = "JWT"): JwtHeader = {
+  def apply(algorithm: String, contentType: String = null, typ: String = "JWT"): JwtHeader = {
     JwtHeader(Option(algorithm), Option(contentType), Option(typ))
   }
 
@@ -44,4 +49,4 @@ object JwtHeader {
   def fromJsonStringOpt(jsonString: String): Option[JwtHeader] = allCatch opt {
     fromJsonString(jsonString)
   }
-}
+}
\ No newline at end of file
diff --git a/src/test/scala/authentikat/jwt/JsonWebTokenSpec.scala b/src/test/scala/authentikat/jwt/JsonWebTokenSpec.scala
index 3798c38..176cd1f 100644
--- a/src/test/scala/authentikat/jwt/JsonWebTokenSpec.scala
+++ b/src/test/scala/authentikat/jwt/JsonWebTokenSpec.scala
@@ -17,6 +17,9 @@ class JsonWebTokenSpec extends FunSpec with Matchers {
 
     it("should have three parts for a token created with claims map claims") {
       val result = JsonWebToken.apply(header, claims, "secretkey")
+      println(result)
+      println(result)
+      println(result)
       result.split("\\.").length should equal(3)
     }
 
@@ -88,6 +91,7 @@ class JsonWebTokenSpec extends FunSpec with Matchers {
   describe("JwtHeader") {
     it("should render to json as per spec") {
       val header = JwtHeader("algorithm", "contentType")
+      println(header.asJsonString)
       val expectedJson = "{\"alg\":\"algorithm\",\"cty\":\"contentType\",\"typ\":\"JWT\"}"
 
       header.asJsonString should equal(expectedJson)
@@ -97,7 +101,7 @@ class JsonWebTokenSpec extends FunSpec with Matchers {
   describe("JwtClaimsSet") {
 
     val date = new Date
-    val dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm'Z'")
+    val dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'")
     dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"))
     val dateIso8601 = dateFormat.format(date)
 
diff --git a/version.sbt b/version.sbt
index 3f81713..cfa5eb7 100644
--- a/version.sbt
+++ b/version.sbt
@@ -1 +1 @@
-version := "0.4.4"
+version := "0.4.5"