diff --git a/pkgs/by-name/ta/tasksh/package.nix b/pkgs/by-name/ta/tasksh/package.nix
index 55a4f6f7e854..9d0e252df021 100644
--- a/pkgs/by-name/ta/tasksh/package.nix
+++ b/pkgs/by-name/ta/tasksh/package.nix
@@ -18,6 +18,11 @@ stdenv.mkDerivation rec {
   buildInputs = [ readline ];
   nativeBuildInputs = [ cmake ];
 
+  cmakeFlags = [
+    # Fix the build with CMake 4.
+    "-DCMAKE_POLICY_VERSION_MINIMUM=3.5"
+  ];
+
   meta = with lib; {
     description = "REPL for taskwarrior";
     homepage = "http://tasktools.org";