diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # ChangeLog for yesod-core
 
+## 1.6.21.0
+
+* Export `Yesod.Core.Dispatch.defaultGen` so that users may reuse it for their own `YesodRunnerEnv`s [#1734](https://github.com/yesodweb/yesod/pull/1734)
+
 ## 1.6.20.2
 
 * Fix compatibility with template-haskell 2.17 [#1729](https://github.com/yesodweb/yesod/pull/1729)
diff --git a/src/Yesod/Core/Dispatch.hs b/src/Yesod/Core/Dispatch.hs
--- a/src/Yesod/Core/Dispatch.hs
+++ b/src/Yesod/Core/Dispatch.hs
@@ -17,6 +17,7 @@
     , mkYesodDispatch
     , mkYesodSubDispatch
       -- *** Helpers
+    , defaultGen
     , getGetMaxExpires
       -- ** Path pieces
     , PathPiece (..)
@@ -100,6 +101,8 @@
 -- unspecified range. The range size may not be a power of 2. Since
 -- 1.6.20, this uses a secure entropy source and generates in the full
 -- range of 'Int'.
+--
+-- @since 1.6.21.0
 defaultGen :: IO Int
 defaultGen = bsToInt <$> getEntropy bytes
   where
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:         1.6.20.2
+version:         1.6.21.0
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>