diff --git a/check-decode-android/src/main/java/org/protowire/check/android/CheckDecodeAndroid.java b/check-decode-android/src/main/java/org/protowire/check/android/CheckDecodeAndroid.java
index fd59f74..5311bcb 100644
--- a/check-decode-android/src/main/java/org/protowire/check/android/CheckDecodeAndroid.java
+++ b/check-decode-android/src/main/java/org/protowire/check/android/CheckDecodeAndroid.java
@@ -62,7 +62,8 @@ public static void main(String[] args) {
                 }
             }
         }
-        PxfMeta meta = METAS.get(schema);
+        // Map.of refuses a null key, and the NPE would exit 1, the reject code.
+        PxfMeta meta = schema == null ? null : METAS.get(schema);
         if (format == null || input == null || meta == null) {
             System.err.println("check-decode-android: need --format, --input and a known --schema, got " + schema);
             System.exit(2);