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:             1.4.0
+version:             1.4.1
 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
@@ -49,6 +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]
 
 newtype Jaeger = Jaeger [Data]