diff --git a/System/Vacuum/Cairo.hs b/System/Vacuum/Cairo.hs
--- a/System/Vacuum/Cairo.hs
+++ b/System/Vacuum/Cairo.hs
@@ -38,6 +38,7 @@
 import Data.Char
 import qualified Control.Exception as C
 
+import System.Directory
 import Control.Concurrent.MVar.Strict
 import System.IO.Unsafe
 import Control.Parallel.Strategies
@@ -158,6 +159,8 @@
                               ,"W8#" ,"W16#" ,"W32#" ,"W64#"] -> showLit n
                  -- chars
                  "C#" -> show . chr . fromIntegral . head . nodeLits $ n
+                 "D#" -> "Double"
+                 "F#" -> "Float"
 
                  -- bytestrings
                  "PS"    -> printf "ByteString[%d,%d]" (nodeLits n !! 1) (nodeLits n !! 2)
@@ -181,7 +184,12 @@
     let dot = render. myPpDot . (showHNodes myStyle) $ vacuum a
 
     -- TODO check for path
-    svgstring <- myReadProcess "dot" ["-Tsvg"] dot
+    mdot <- findExecutable "dot" 
+    let exe = case mdot of
+                Nothing -> error "\"dot\" executable not found. Please install graphviz"
+                Just p  -> p
+
+    svgstring <- myReadProcess exe ["-Tsvg"] dot
     svg       <- C.svgNewFromString svgstring
     writeFile "/tmp/demo" svgstring
 
diff --git a/vacuum-cairo.cabal b/vacuum-cairo.cabal
--- a/vacuum-cairo.cabal
+++ b/vacuum-cairo.cabal
@@ -1,5 +1,5 @@
 name:               vacuum-cairo
-version:            0.3
+version:            0.3.1
 cabal-version:      >= 1.2
 build-type:         Simple
 license:            BSD3
@@ -26,13 +26,15 @@
                     <http://code.haskell.org/~dons/images/vacuum/intmap.png>
 
 library
-  build-depends:    base >= 3,
-                    vacuum >= 0.0.5,
+  build-depends:    base >= 3 && < 4,
+                    vacuum >= 0.0.5.1,
                     gtk,
-                    parallel,
-                    strict-concurrency,
                     cairo,
                     svgcairo,
                     process,
-                    pretty
+                    pretty,
+                    directory,
+                    parallel,
+                    strict-concurrency
+
   exposed-modules:  System.Vacuum.Cairo