diff --git a/pkgs/applications/science/astronomy/calcmysky/default.nix b/pkgs/applications/science/astronomy/calcmysky/default.nix
index 83d98590828d..3b66284e8b0c 100644
--- a/pkgs/applications/science/astronomy/calcmysky/default.nix
+++ b/pkgs/applications/science/astronomy/calcmysky/default.nix
@@ -22,6 +22,8 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake wrapQtAppsHook ];
   buildInputs = [ glm eigen qtbase ];
 
+  cmakeFlags = [ "-DQT_VERSION=6" ];
+
   doCheck = true;
 
   meta = with lib;{
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 9456fdfe6487..8c63cca9c806 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -27514,7 +27514,7 @@ with pkgs;
       inherit (gnome2) libglade;
   };
 
-  calcmysky = libsForQt5.callPackage ../applications/science/astronomy/calcmysky { };
+  calcmysky = qt6Packages.callPackage ../applications/science/astronomy/calcmysky { };
 
   calcurse = callPackage ../applications/misc/calcurse { };