diff --git a/scripts/install-nix-from-closure.sh b/scripts/install-nix-from-closure.sh
index 6efd8af18..14fb91534 100644
--- a/scripts/install-nix-from-closure.sh
+++ b/scripts/install-nix-from-closure.sh
@@ -2,6 +2,8 @@
 
 set -e
 
+umask 0022
+
 dest="/nix"
 self="$(dirname "$0")"
 nix="@nix@"
diff --git a/scripts/install.in b/scripts/install.in
index 1d26c4ff0..39fae37e3 100644
--- a/scripts/install.in
+++ b/scripts/install.in
@@ -10,6 +10,8 @@ oops() {
     exit 1
 }
 
+umask 0022
+
 tmpDir="$(mktemp -d -t nix-binary-tarball-unpack.XXXXXXXXXX || \
           oops "Can't create temporary directory for downloading the Nix binary tarball")"
 cleanup() {