diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,7 @@
+## 0.1.1.3 (2017-10-10)
+
+ * Fix a space leak in `System.Metric.Label.set` ([#21](https://github.com/tibbe/ekg-core/pull/21)).
+
 ## 0.1.1.2 (2017-07-31)
 
  * GHC 8.2 support.
diff --git a/System/Metrics/Label.hs b/System/Metrics/Label.hs
--- a/System/Metrics/Label.hs
+++ b/System/Metrics/Label.hs
@@ -12,7 +12,7 @@
     , modify
     ) where
 
-import Data.IORef (IORef, atomicModifyIORef, newIORef, readIORef)
+import Data.IORef (IORef, atomicModifyIORef', atomicWriteIORef, newIORef, readIORef)
 import qualified Data.Text as T
 import Prelude hiding (read)
 
@@ -29,11 +29,9 @@
 
 -- | Set the label to the given value.
 set :: Label -> T.Text -> IO ()
-set (C ref) !i = atomicModifyIORef ref $ \ _ -> (i, ())
+set (C ref) !i = atomicWriteIORef ref i
 
 -- | Set the label to the result of applying the given function to the
 -- value.
 modify :: (T.Text -> T.Text) -> Label -> IO ()
-modify f (C ref) = do
-    !_ <- atomicModifyIORef ref $ \ i -> let i' = f i in (i', i')
-    return ()
+modify f (C ref) = atomicModifyIORef' ref $ \i -> (f i, ())
diff --git a/ekg-core.cabal b/ekg-core.cabal
--- a/ekg-core.cabal
+++ b/ekg-core.cabal
@@ -1,5 +1,5 @@
 name:                ekg-core
-version:             0.1.1.2
+version:             0.1.1.3
 synopsis:            Tracking of system metrics
 description:
   This library lets you defined and track system metrics.
@@ -8,7 +8,8 @@
 license:             BSD3
 license-file:        LICENSE
 author:              Johan Tibell
-maintainer:          johan.tibell@gmail.com
+maintainer:          Johan Tibell <johan.tibell@gmail.com>,
+                     Mikhail Glushenkov <mikhail.glushenkov@gmail.com>
 category:            System
 build-type:          Simple
 extra-source-files:  CHANGES.md