diff --git a/build_tools/make_pkg.sh b/build_tools/make_pkg.sh
index 8d07562db..edd17747a 100755
--- a/build_tools/make_pkg.sh
+++ b/build_tools/make_pkg.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 # Script to produce an OS X installer .pkg and .app(.zip)
 
@@ -17,19 +17,23 @@ set -x
 #Exit on error
 set -e
 
+# Respect MAC_CODESIGN_ID and MAC_PRODUCTSIGN_ID, or default for ad-hoc.
+# Note the :- means "or default" and the following - is the value.
+MAC_CODESIGN_ID=${MAC_CODESIGN_ID:--}
+MAC_PRODUCTSIGN_ID=${MAC_PRODUCTSIGN_ID:--}
+
 PKGDIR=$(mktemp -d)
 
 SRC_DIR=$PWD
 OUTPUT_PATH=${FISH_ARTEFACT_PATH:-~/fish_built}
 
 mkdir -p "$PKGDIR/build" "$PKGDIR/root" "$PKGDIR/intermediates" "$PKGDIR/dst"
-{ cd "$PKGDIR/build" && cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo "$SRC_DIR" && make -j 4 && env DESTDIR="$PKGDIR/root/" make install; }
+{ cd "$PKGDIR/build" && cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DMAC_CODESIGN_ID="${MAC_CODESIGN_ID}" "$SRC_DIR" && make -j 12 && env DESTDIR="$PKGDIR/root/" make install; }
 pkgbuild --scripts "$SRC_DIR/build_tools/osx_package_scripts" --root "$PKGDIR/root/" --identifier 'com.ridiculousfish.fish-shell-pkg' --version "$VERSION" "$PKGDIR/intermediates/fish.pkg"
-
 productbuild  --package-path "$PKGDIR/intermediates" --distribution "$SRC_DIR/build_tools/osx_distribution.xml" --resources "$SRC_DIR/build_tools/osx_package_resources/" "$OUTPUT_PATH/fish-$VERSION.pkg"
-
+productsign --sign "${MAC_PRODUCTSIGN_ID}" "$OUTPUT_PATH/fish-$VERSION.pkg" "$OUTPUT_PATH/fish-$VERSION-signed.pkg" && mv "$OUTPUT_PATH/fish-$VERSION-signed.pkg" "$OUTPUT_PATH/fish-$VERSION.pkg"
 
 # Make the app
-{ cd "$PKGDIR/build" && make fish_macapp && zip -r "$OUTPUT_PATH/fish-$VERSION.app.zip" fish.app; }
+{ cd "$PKGDIR/build" && make signed_fish_macapp && zip -r "$OUTPUT_PATH/fish-$VERSION.app.zip" fish.app; }
 
 rm -r "$PKGDIR"