diff --git a/pkgs/build-support/docker/default.nix b/pkgs/build-support/docker/default.nix
index 9a20df57777c..1b6c340f7f0c 100644
--- a/pkgs/build-support/docker/default.nix
+++ b/pkgs/build-support/docker/default.nix
@@ -240,7 +240,7 @@ rec {
           # Unpack all of the parent layers into the image.
           lowerdir=""
           extractionID=0
-          for layerTar in $(tac layer-list); do
+          for layerTar in $(cat layer-list); do
             echo "Unpacking layer $layerTar"
             extractionID=$((extractionID + 1))