diff --git a/derivation/src/main/scala/io/bullet/borer/derivation/MapBasedCodecs.scala b/derivation/src/main/scala/io/bullet/borer/derivation/MapBasedCodecs.scala
index 73f40d9d..a5c5c872 100644
--- a/derivation/src/main/scala/io/bullet/borer/derivation/MapBasedCodecs.scala
+++ b/derivation/src/main/scala/io/bullet/borer/derivation/MapBasedCodecs.scala
@@ -166,7 +166,7 @@ object MapBasedCodecs {
               val key           = p.key()
               val writeKey      = q"w.${TermName(s"write${key.productPrefix}")}(${literal(key.value)})"
               val isBasic       = basicParams contains p
-              val method        = TermName(s"write${if (isBasic) p.paramType.tpe.toString else ""}")
+              val method        = TermName(s"write${if (isBasic) p.paramType.tpe.dealias.toString else ""}")
               val rawWriteEntry = q"$writeKey.$method(value.${p.name})"
               if (isBasic) {
                 if (p.defaultValueMethod.isDefined) q"if (${encName(p, "o")}) $rawWriteEntry" else rawWriteEntry
@@ -251,7 +251,7 @@ object MapBasedCodecs {
               params.filterNot(p => p.isBasicType && decodersForParams(p).exists(isDefinedOn(_, decoderCompanion)))
 
             def readField(p: CaseParam) = {
-              val tpe = p.paramType.tpe
+              val tpe = p.paramType.tpe.dealias
               if (nonBasicParams contains p) q"r.read[$tpe]()(${decName(p)})" else q"r.${TermName(s"read$tpe")}()"
             }
 
diff --git a/derivation/src/test/scala/io/bullet/borer/derivation/MiscSpec.scala b/derivation/src/test/scala/io/bullet/borer/derivation/MiscSpec.scala
index a1b1e365..53247598 100644
--- a/derivation/src/test/scala/io/bullet/borer/derivation/MiscSpec.scala
+++ b/derivation/src/test/scala/io/bullet/borer/derivation/MiscSpec.scala
@@ -107,10 +107,18 @@ object MiscSpec extends AbstractBorerSpec {
 
     "Custom 'Unit' type" - {
       sealed trait Unit
-      implicit val unitDecoder: Decoder[Unit] = Decoder(_ => null)
+      implicit val unitDecoder: Decoder[Unit] = Decoder { r => r.readNull(); null }
 
       final case class Foo(value: Double, unit: Unit)
       implicit val fooDecoder: Decoder[Foo] = MapBasedCodecs.deriveDecoder
+      verifyDecoding("null", null)
+    }
+
+    "Type alias" - {
+      type Foo = String
+      case class Bar(bar: Foo)
+      implicit val barCodec: Codec[Bar] = MapBasedCodecs.deriveCodec
+      roundTrip("""{"bar":"yeah"}""", Bar("yeah"))
     }
   }
 }