diff --git a/pkgs/by-name/ca/calibre/package.nix b/pkgs/by-name/ca/calibre/package.nix
index 3da071d9b4d6..0f5c8dead6cc 100644
--- a/pkgs/by-name/ca/calibre/package.nix
+++ b/pkgs/by-name/ca/calibre/package.nix
@@ -184,6 +184,9 @@ stdenv.mkDerivation (finalAttrs: {
   installPhase = ''
     runHook preInstall
 
+    # Work around #493843 until #493988 lands on master.
+    export QMAKE="${qt6.qtbase}/bin/qmake"
+
     python setup.py install --root=$out \
       --prefix=$out \
       --libdir=$out/lib \