diff --git a/datadog-tracing.cabal b/datadog-tracing.cabal
--- a/datadog-tracing.cabal
+++ b/datadog-tracing.cabal
@@ -1,6 +1,6 @@
 cabal-version:       2.2
 name:                datadog-tracing
-version:             1.4.1
+version:             1.4.2
 synopsis:            Datadog tracing client and mock agent.
 license:             BSD-3-Clause
 license-file:        LICENSE
diff --git a/library/Datadog/Jaeger.hs b/library/Datadog/Jaeger.hs
--- a/library/Datadog/Jaeger.hs
+++ b/library/Datadog/Jaeger.hs
@@ -49,8 +49,7 @@
               (ProcessID spanService)
     services spans = nub $ Agent.spanService <$> spans
     showt = T.pack . show
-    mkTag (k, "true") = Tag k -- magic value skips concatenation
-    mkTag (k, v) = Tag $ T.concat [k, ":", v]
+    mkTag (k, v) = Tag k v
 
 newtype Jaeger = Jaeger [Data]
 instance ToJSON Jaeger where
@@ -87,7 +86,8 @@
   , spanID  :: SpanID
   } deriving (Eq, Ord, Generic, ToJSON)
 
-newtype Tag = Tag
-  { key :: Text
+data Tag = Tag
+  { key   :: Text
+  , value :: Text
   } deriving (Eq, Generic)
     deriving anyclass (ToJSON)