diff --git a/containers/shower/default.nix b/containers/shower/default.nix
index 6e97d6b..4d055bf 100644
--- a/containers/shower/default.nix
+++ b/containers/shower/default.nix
@@ -82,10 +82,16 @@ let
 
       ${python}/bin/python -m venv "$TMPDIR/venv"
       "$TMPDIR/venv/bin/pip" install --upgrade pip
+
+      # Nix store paths embed a 32-char hash prefix, which pip's wheel
+      # filename parser rejects ("Invalid wheel filename"). Copy to a
+      # clean filename in TMPDIR before installing.
+      cp ${showerWheel} "$TMPDIR/${showerWheel.name}"
+
       "$TMPDIR/venv/bin/pip" install \
         --no-cache-dir \
         --index-url=https://pypi.ops.eblu.me/root/pypi/+simple/ \
-        ${showerWheel} \
+        "$TMPDIR/${showerWheel.name}" \
         gunicorn
 
       runHook postBuild