diff --git a/tools/test-install.sh b/tools/test-install.sh
index b618ac8..0dcb3eb 100755
--- a/tools/test-install.sh
+++ b/tools/test-install.sh
@@ -63,12 +63,21 @@ if df --output=fstype "$TARGET_DIR" | tail -1 | grep -q tmpfs; then
 fi
 
 OVMF="${NOMARCHY_OVMF:-}"
-[ -n "$OVMF" ] || for c in /run/current-system/sw/share/qemu/edk2-x86_64-code.fd \
-         /run/current-system/sw/share/OVMF/OVMF_CODE.fd \
-         /usr/share/OVMF/OVMF_CODE.fd; do
-    [ -f "$c" ] && { OVMF="$c"; break; }
-done
-[ -n "$OVMF" ] || { echo "no OVMF firmware found" >&2; exit 1; }
+if [ -z "$OVMF" ]; then
+    for c in /run/current-system/sw/share/qemu/edk2-x86_64-code.fd \
+             /run/current-system/sw/share/OVMF/OVMF_CODE.fd \
+             /usr/share/OVMF/OVMF_CODE.fd; do
+        [ -f "$c" ] && { OVMF="$c"; break; }
+    done
+fi
+# Fall back to nixpkgs OVMF.fd (FV/OVMF_CODE.fd) when not on the host profile.
+if [ -z "$OVMF" ] || [ ! -f "$OVMF" ]; then
+    ovmf_store=$(nix build --no-link --print-out-paths nixpkgs#OVMF.fd 2>/dev/null || true)
+    for c in "$ovmf_store"/FV/OVMF_CODE.fd "$ovmf_store"/FV/OVMF.fd; do
+        [ -f "$c" ] && { OVMF="$c"; break; }
+    done
+fi
+[ -n "$OVMF" ] && [ -f "$OVMF" ] || { echo "no OVMF firmware found (set NOMARCHY_OVMF=…)" >&2; exit 1; }
 
 echo "==> Building the live ISO..."
 nix build .#nixosConfigurations.nomarchy-live.config.system.build.isoImage