diff --git a/pkgs/development/libraries/ndi/default.nix b/pkgs/development/libraries/ndi/default.nix
index 1c15455b6ad..9cd0d186302 100644
--- a/pkgs/development/libraries/ndi/default.nix
+++ b/pkgs/development/libraries/ndi/default.nix
@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
   buildInputs = [ avahi ];
 
   unpackPhase = ''
-    unpackFile ${src}
+    unpackFile $src
     echo y | ./${installerName}.sh
     sourceRoot="NDI SDK for Linux";
   '';