diff --git a/hgeos.cabal b/hgeos.cabal
--- a/hgeos.cabal
+++ b/hgeos.cabal
@@ -1,5 +1,5 @@
 name:                 hgeos
-version:              0.1.7.1
+version:              0.1.7.2
 synopsis:             Simple Haskell bindings to GEOS C API
 description:
   Simple Haskell bindings to the <https://trac.osgeo.org/geos/ GEOS>
diff --git a/src/lib/Data/Geolocation/GEOS.hs b/src/lib/Data/Geolocation/GEOS.hs
--- a/src/lib/Data/Geolocation/GEOS.hs
+++ b/src/lib/Data/Geolocation/GEOS.hs
@@ -7,8 +7,9 @@
 Stability   : experimental
 Portability : portable
 
-A high-level API for interoperating with GEOS C API which includes automatic
-management of lifetimes of objects such as readers, writers and geometries.
+A high-level API for interoperating with Geometry Engine Open Source C API
+which includes automatic management of lifetimes of objects such as readers,
+writers and geometries.
 
 For the low-level FFI bindings, see "Data.Geolocation.GEOS.Imports".
 
@@ -160,14 +161,14 @@
 -- sequence
 createLinearRing :: CoordinateSequence -> IO (Maybe Geometry)
 createLinearRing (CoordinateSequence sr deleteAction h) = do
-    untrack sr deleteAction
+    untrack sr [deleteAction]
     checkAndTrackGeometry sr (\hCtx -> c_GEOSGeom_createLinearRing_r hCtx h)
 
 -- |Returns a polygon 'Geometry' instance from the given shell and optional
 -- array of holes
 createPolygon :: Geometry -> [Geometry] -> IO (Maybe Geometry)
 createPolygon (Geometry sr deleteAction h) holes = do
-    untrack sr deleteAction
+    untrack sr (deleteAction : map (\(Geometry _ x _) -> x) holes)
     withArrayLen (map (\(Geometry _ _ h') -> h') holes) $ \count array ->
         checkAndTrackGeometry
             sr
@@ -339,9 +340,10 @@
 setZ :: CoordinateSequence -> Word -> Double -> IO (Maybe ())
 setZ = setOrdinateHelper c_GEOSCoordSeq_setZ_r
 
-untrack :: ContextStateRef -> DeleteAction -> IO ()
-untrack sr (DeleteAction rawPtr _) =
-    modifyIORef' sr $ \p@ContextState{..} -> p { deleteActions = filter (\(DeleteAction r _) -> r /= rawPtr) deleteActions }
+untrack :: ContextStateRef -> [DeleteAction] -> IO ()
+untrack sr deleteActions = do
+    let rawPtrs = map (\(DeleteAction rawPtr _) -> rawPtr) deleteActions
+    modifyIORef' sr $ \p@ContextState{..} -> p { deleteActions = filter (\(DeleteAction rawPtr _) -> not (rawPtr `elem` rawPtrs)) deleteActions }
 
 -- |Reports version of GEOS API
 version :: IO String
diff --git a/src/lib/Data/Geolocation/GEOS/Imports.hs b/src/lib/Data/Geolocation/GEOS/Imports.hs
--- a/src/lib/Data/Geolocation/GEOS/Imports.hs
+++ b/src/lib/Data/Geolocation/GEOS/Imports.hs
@@ -7,10 +7,10 @@
 Stability   : experimental
 Portability : portable
 
-These are low-level FFI bindings for the GEOS C API derived from
-<http://geos.osgeo.org/doxygen/geos__c_8h_source.html geos_c.h>. These enable
-low-level access to the native functions for parts of the C API for which
-high-level wrappers do not yet exist.
+These are low-level FFI bindings for the Geometry Engine Open Source C API
+derived from <http://geos.osgeo.org/doxygen/geos__c_8h_source.html geos_c.h>.
+These enable low-level access to the native functions for parts of the C API
+for which high-level wrappers do not yet exist.
 
 For the high-level API, see "Data.Geolocation.GEOS".
 
diff --git a/src/lib/Data/Geolocation/GEOS/helpers.c b/src/lib/Data/Geolocation/GEOS/helpers.c
--- a/src/lib/Data/Geolocation/GEOS/helpers.c
+++ b/src/lib/Data/Geolocation/GEOS/helpers.c
@@ -1,3 +1,13 @@
+/*
+Module      : helpers.c
+Description : C helper functions for hgeos
+Copyright   : (C) Richard Cook, 2016
+Licence     : MIT
+Maintainer  : rcook@rcook.org
+Stability   : experimental
+Portability : portable
+*/
+
 #include <geos_c.h>
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/src/test/GEOSTest/TransAPI.hs b/src/test/GEOSTest/TransAPI.hs
--- a/src/test/GEOSTest/TransAPI.hs
+++ b/src/test/GEOSTest/TransAPI.hs
@@ -3,6 +3,7 @@
 import Control.Monad
 import Control.Monad.Trans
 import Control.Monad.Trans.Maybe
+import Data.Geolocation.GEOS (Context, Geometry)
 import Data.Geolocation.GEOS.Trans
 import Data.Maybe
 
@@ -10,6 +11,17 @@
 check True = return ()
 check False = error "Check failed"
 
+type Coordinate = (Double, Double)
+
+createLinearRing :: Context -> [Coordinate] -> MaybeT IO Geometry
+createLinearRing ctx cs = do
+    let count = length cs
+    coords <- createCoordSeqM ctx (fromIntegral count) 2
+    forM_ (zip [0..] cs) $ \(i, (x, y)) -> do
+        setXM coords i x
+        setYM coords i y
+    createLinearRingM coords
+
 -- Demonstrates use of monad transformer API
 -- Lifetimes of GEOS objects are automatically managed by the context objects
 -- which guarantees that they are released when the context goes out of scope
@@ -55,6 +67,12 @@
         p <- createPolygonM g3 []
         str2 <- writeGeometryM writer p
         lift $ putStrLn str2
+
+        shell <- createLinearRing ctx [(-10.0, -10.0), (-10.0, 10.0), (10.0, 10.0), (10.0, -10.0), (-10.0, -10.0)]
+        hole <- createLinearRing ctx [(-5.0, -5.0), (-5.0, 5.0), (5.0, 5.0), (5.0, -5.0), (-5.0, -5.0)]
+        polygon <- createPolygonM shell [hole]
+        str3 <- writeGeometryM writer polygon
+        lift $ putStrLn str3
 
     case result of
          Left m -> error $ "TransAPI.demo failed: " ++ m