diff --git a/pkgs/build-support/vm/default.nix b/pkgs/build-support/vm/default.nix
index 1a80592a40e5..4e935feba15b 100644
--- a/pkgs/build-support/vm/default.nix
+++ b/pkgs/build-support/vm/default.nix
@@ -423,7 +423,7 @@ rec {
         set +o pipefail
         for i in $rpms; do
             echo "$i..."
-            ${rpm}/bin/rpm2cpio "$i" | chroot /mnt ${cpio}/bin/cpio -i --make-directories
+            ${rpm}/bin/rpm2cpio "$i" | chroot /mnt ${cpio}/bin/cpio -i --make-directories --unconditional
         done
 
         eval "$preInstall"
@@ -438,7 +438,7 @@ rec {
 
         echo "installing RPMs..."
         PATH=/usr/bin:/bin:/usr/sbin:/sbin $chroot /mnt \
-          rpm -iv ${if runScripts then "" else "--noscripts"} $rpms
+          rpm -iv --nosignature ${if runScripts then "" else "--noscripts"} $rpms
 
         echo "running post-install script..."
         eval "$postInstall"