diff --git a/Data/GraphViz/Commands.hs b/Data/GraphViz/Commands.hs
index 20e7dbe..514c29d 100644
--- a/Data/GraphViz/Commands.hs
+++ b/Data/GraphViz/Commands.hs
@@ -63,14 +63,14 @@ import           System.IO        (Handle, hPutStrLn, hSetBinaryMode, stderr)
 -- -----------------------------------------------------------------------------
 
 showCmd           :: GraphvizCommand -> String
-showCmd Dot       = "dot"
-showCmd Neato     = "neato"
-showCmd TwoPi     = "twopi"
-showCmd Circo     = "circo"
-showCmd Fdp       = "fdp"
-showCmd Sfdp      = "sfdp"
-showCmd Osage     = "osage"
-showCmd Patchwork = "patchwork"
+showCmd Dot       = "@graphviz@/bin/dot"
+showCmd Neato     = "@graphviz@/bin/neato"
+showCmd TwoPi     = "@graphviz@/bin/twopi"
+showCmd Circo     = "@graphviz@/bin/circo"
+showCmd Fdp       = "@graphviz@/bin/fdp"
+showCmd Sfdp      = "@graphviz@/bin/sfdp"
+showCmd Osage     = "@graphviz@/bin/osage"
+showCmd Patchwork = "@graphviz@/bin/patchwork"
 
 -- | The default command for directed graphs.
 dirCommand :: GraphvizCommand
@@ -312,8 +312,11 @@ runGraphvizCanvas' d = runGraphvizCanvas (commandFor d) d
 
 -- | Is the Graphviz suite of tools installed?  This is determined by
 --   whether @dot@ is available in the @PATH@.
+--
+--   Note: With nixpkgs, this will always return 'True' as graphviz'
+--   store paths are hardcoded instead of looking at @PATH@.
 isGraphvizInstalled :: IO Bool
-isGraphvizInstalled = liftM isJust . findExecutable $ showCmd Dot
+isGraphvizInstalled = pure True -- :)
 
 -- | If Graphviz does not seem to be available, print the provided
 --   error message and then exit fatally.