diff --git a/pkgs/build-support/build-fhsenv-bubblewrap/default.nix b/pkgs/build-support/build-fhsenv-bubblewrap/default.nix
index 99faeb7eb01af..5be1172352b5a 100644
--- a/pkgs/build-support/build-fhsenv-bubblewrap/default.nix
+++ b/pkgs/build-support/build-fhsenv-bubblewrap/default.nix
@@ -126,12 +126,13 @@ let
 
   indentLines = str: concatLines (map (s: "  " + s) (filter (s: s != "") (splitString "\n" str)));
   bwrapCmd = { initArgs ? "" }: ''
-    ${extraPreBwrapCmds}
     ignored=(/nix /dev /proc /etc ${optionalString privateTmp "/tmp"})
     ro_mounts=()
     symlinks=()
     etc_ignored=()
 
+    ${extraPreBwrapCmds}
+
     # loop through all entries of root in the fhs environment, except its /etc.
     for i in ${fhsenv}/*; do
       path="/''${i##*/}"