diff --git a/pkgs/development/tools/analysis/spin/default.nix b/pkgs/development/tools/analysis/spin/default.nix
index f1295060d3c..29559bf8b0e 100644
--- a/pkgs/development/tools/analysis/spin/default.nix
+++ b/pkgs/development/tools/analysis/spin/default.nix
@@ -2,13 +2,15 @@
 
 stdenv.mkDerivation rec {
   name = "spin-${version}";
-  version = "6.4.3";
+  version = "6.4.5";
   url-version = stdenv.lib.replaceChars ["."] [""] version;
 
   src = fetchurl {
-    url = "http://spinroot.com/spin/Src/spin${url-version}.tar.gz";
-    curlOpts = "--user-agent 'Mozilla/5.0'";
-    sha256 = "0cldhxvfw6llh4spcx0x0535pffx89pvvxpdi0bpqy9a6da85ln1";
+    # The homepage is behind CloudFlare anti-DDoS protection, which blocks cURL.
+    # Dropbox mirror from developers:
+    # https://www.dropbox.com/sh/fgzipzp4wpo3qc1/AADZPqS4aoR-pjNF6OQXRLQHa
+    url = "https://www.dropbox.com/sh/fgzipzp4wpo3qc1/AAANRpxsSyWC7iHZB-XgBwJFa/spin645.tar.gz?raw=1";
+    sha256 = "0x8qnwm2xa8f176c52mzpvnfzglxs6xgig7bcgvrvkb3xf114224";
   };
 
   buildInputs = [ yacc ];
@@ -20,7 +22,8 @@ stdenv.mkDerivation rec {
   meta = with stdenv.lib; {
     description = "Formal verification tool for distributed software systems";
     homepage = http://spinroot.com/;
-    license = stdenv.lib.licenses.free;
+    license = licenses.free;
+    platforms = platforms.linux;
     maintainers = with maintainers; [ mornfall pSub ];
   };
 }