diff --git a/pkgs/os-specific/linux/otpw/default.nix b/pkgs/os-specific/linux/otpw/default.nix
index 97b601be24cf..423950be5392 100644
--- a/pkgs/os-specific/linux/otpw/default.nix
+++ b/pkgs/os-specific/linux/otpw/default.nix
@@ -4,7 +4,7 @@ stdenv.mkDerivation {
   name = "otpw-1.3";
 
   src = fetchurl {
-    url = ttp://www.cl.cam.ac.uk/~mgk25/download/otpw-1.3.tar.gz;
+    url = http://www.cl.cam.ac.uk/~mgk25/download/otpw-1.3.tar.gz;
     sha256 = "1k3hc7xbxz6hkc55kvddi3cibafwf93ivn58sy1l888d3l5dwmrk";
   };