diff --git a/pkgs/tools/graphics/pfstools/default.nix b/pkgs/tools/graphics/pfstools/default.nix
index 6dafbfe2f9fe..6a0385614e87 100644
--- a/pkgs/tools/graphics/pfstools/default.nix
+++ b/pkgs/tools/graphics/pfstools/default.nix
@@ -14,9 +14,7 @@ stdenv.mkDerivation rec {
 
   outputs = [ "out" "dev" "man"];
 
-  cmakeFlags = ''
-    -DWITH_MATLAB=false 
-  '';
+  cmakeFlags = [ "-DWITH_MATLAB=false" ];
 
   preConfigure = ''
     rm cmake/FindNETPBM.cmake