diff --git a/codegen.sh b/codegen.sh
index 088a94186..c0d2c7dae 100755
--- a/codegen.sh
+++ b/codegen.sh
@@ -9,7 +9,7 @@ for SPEC in $SPECS; do
 
 	SRC=$(dirname $(dirname $SPEC))
 	echo "=== codegen $SRC ==="
-	GOPATHS=$(codegen/codegen.php $(basename $SRC) | tee -a /dev/stderr | xargs -n1 dirname | sort | uniq)
+	GOPATHS=$(codegen/codegen.php $(basename $SRC) | tee -a /dev/stderr | xargs --no-run-if-empty -n1 dirname | sort | uniq)
 	for FOLDER in $GOPATHS; do
 		if [[ $FOLDER != "." ]]; then
 			echo "== go fmt $FOLDER =="
diff --git a/codegen/codegen.php b/codegen/codegen.php
index 46ea76e21..2b9aa6759 100755
--- a/codegen/codegen.php
+++ b/codegen/codegen.php
@@ -45,6 +45,10 @@ $tpl->add_default("newline", "\n");
 $generators = array();
 exec("find -L " . __DIR__ . "/" . $project . " -name index.php", $generators);
 
+if (getenv("DEBUG") === "true") {
+	fprintf(STDERR, print_r($generators, true));
+}
+
 $api_files = glob($project . "/docs/src/spec/*.json");
 $apis = array_map(function($filename) {
 	$api = array_change_key_case_recursive(json_decode(file_get_contents($filename), true));
@@ -87,6 +91,9 @@ foreach ($generators as $generator) {
 		mkdir($dirname, 0777, true);
 	}
 	$common = compact("parsers", "project");
+	if (getenv("DEBUG") === "true") {
+		fprintf(STDERR, print_r($common, true));
+	}
 	include($generator);
 }