diff --git a/trusty/keymaster/trusty_keymaster_device.cpp b/trusty/keymaster/trusty_keymaster_device.cpp
index 5f16fd0..cfe94cc 100644
--- a/trusty/keymaster/trusty_keymaster_device.cpp
+++ b/trusty/keymaster/trusty_keymaster_device.cpp
@@ -576,7 +576,9 @@
         return error_;
     }
     if (input && input->data_length > kMaximumFinishInputLength) {
-        return KM_ERROR_INVALID_ARGUMENT;
+        ALOGE("%zu-byte input to finish; only %zu bytes allowed",
+              input->data_length, kMaximumFinishInputLength);
+        return KM_ERROR_INVALID_INPUT_LENGTH;
     }
 
     if (out_params) {