diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,8 @@
+## 1.6.2
+
+* Derive a `Show` instance for `ResourceTree` and `FlatResource` [#1492](https://github.com/yesodweb/yesod/pull/1492)
+	* Some third party packages, like `yesod-routes-flow` derive their own `Show` instance, and this will break those packages.
+
 ## 1.6.1
 
 * Add a `Semigroup LiteApp` instance, and explicitly define `(<>)` in the
diff --git a/Yesod/Routes/TH/Types.hs b/Yesod/Routes/TH/Types.hs
--- a/Yesod/Routes/TH/Types.hs
+++ b/Yesod/Routes/TH/Types.hs
@@ -21,7 +21,7 @@
 data ResourceTree typ
     = ResourceLeaf (Resource typ)
     | ResourceParent String CheckOverlap [Piece typ] [ResourceTree typ]
-    deriving Functor
+    deriving (Show, Functor)
 
 resourceTreePieces :: ResourceTree typ -> [Piece typ]
 resourceTreePieces (ResourceLeaf r) = resourcePieces r
@@ -90,7 +90,7 @@
     , frPieces :: [Piece a]
     , frDispatch :: Dispatch a
     , frCheck :: Bool
-    }
+    } deriving (Show)
 
 flatten :: [ResourceTree a] -> [FlatResource a]
 flatten =
diff --git a/yesod-core.cabal b/yesod-core.cabal
--- a/yesod-core.cabal
+++ b/yesod-core.cabal
@@ -1,5 +1,5 @@
 name:            yesod-core
-version:         1.6.1
+version:         1.6.2
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>