diff --git a/Makefile b/Makefile
index c44637d..23b88f1 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ $(OUT)ppkb-usb-debugger: usb-debugger.c common.c
 
 $(OUT)kmap.h: keymaps/physical-map.txt keymaps/factory-keymap.txt
 	@mkdir -p $(OUT)
-	php keymaps/map-to-c.php $^ > $@
+	php keymaps/map-to-c.php $^ $@
 
 $(OUT)ppkb-i2c-inputd: i2c-inputd.c $(OUT)kmap.h common.c
 	@mkdir -p $(OUT)
diff --git a/keymaps/map-to-c.php b/keymaps/map-to-c.php
index 681e962..1a99327 100644
--- a/keymaps/map-to-c.php
+++ b/keymaps/map-to-c.php
@@ -20,9 +20,23 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+set_error_handler(function($severity, $message, $file, $line) {
+	if (!(error_reporting() & $severity))
+		return;
+
+	throw new ErrorException($message, 0, $severity, $file, $line);
+});
+
+if (count($argv) != 4) {
+	echo "Usage: $argv[0] <physmap> <keymap> <output>\n";
+	exit(1);
+}
+
 $pmap = file_get_contents($argv[1]);
 $kmap = file_get_contents($argv[2]);
 
+ob_start();
+
 // high nibble = row, low nibble col
 $el_phys_map = [];
 foreach (explode("\n", $pmap) as $ln) {
@@ -100,3 +114,6 @@ function kmap_to_code($name, $map) {
 kmap_to_code("keymap_base", $phys_key_base);
 kmap_to_code("keymap_fn", $phys_key_fn);
 kmap_to_code("keymap_pine", $phys_key_pine);
+
+file_put_contents($argv[3], ob_get_contents());
+ob_end_clean();