diff --git a/CHANGES.md b/CHANGES.md
index cd7b88e..f0d3157 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,10 @@
     causing some floating windows to be smaller/larger than the size they
     requested.
 
+  * Added `Typeable layout` constraint to `LayoutClass`, making it possible to
+    cast `Layout` back into a concrete type and extract current layout state
+    from it.
+
 ## 0.15 (September 30, 2018)
 
   * Reimplement `sendMessage` to deal properly with windowset changes made
diff --git a/src/XMonad/Core.hs b/src/XMonad/Core.hs
index 7810522..96a9878 100644
--- a/src/XMonad/Core.hs
+++ b/src/XMonad/Core.hs
@@ -271,7 +271,7 @@ readsLayout (Layout l) s = [(Layout (asTypeOf x l), rs) | (x, rs) <- reads s]
 -- 'runLayout', 'handleMessage', and so on.  This ensures that the
 -- proper methods will be used, regardless of the particular methods
 -- that any 'LayoutClass' instance chooses to define.
-class Show (layout a) => LayoutClass layout a where
+class (Show (layout a), Typeable layout) => LayoutClass layout a where
 
     -- | By default, 'runLayout' calls 'doLayout' if there are any
     --   windows to be laid out, and 'emptyLayout' otherwise.  Most