diff --git a/pkgs/development/tools/misc/gnum4/default.nix b/pkgs/development/tools/misc/gnum4/default.nix
index 12cc50a37a00..8d3d175e730f 100644
--- a/pkgs/development/tools/misc/gnum4/default.nix
+++ b/pkgs/development/tools/misc/gnum4/default.nix
@@ -8,7 +8,8 @@ stdenv.mkDerivation {
     sha256 = "035r7ma272j2cwni2961jp22k6bn3n9xwn3b3qbcn2yrvlghql22";
   };
 
-  doCheck = !stdenv.isDarwin;
+  doCheck = !stdenv.isDarwin
+    && !stdenv.isCygwin;                   # XXX: `test-dup2' fails on Cygwin
 
   # Upstream is aware of it; it may be in the next release.
   patches = [ ./s_isdir.patch ./readlink-EINVAL.patch ];