diff --git a/aos/json_tokenizer.cc b/aos/json_tokenizer.cc
index e2e8f37..ac519c8 100644
--- a/aos/json_tokenizer.cc
+++ b/aos/json_tokenizer.cc
@@ -356,6 +356,7 @@
               ConsumeWhitespace();
               state_ = State::kExpectObjectEnd;
             } else {
+              fprintf(stderr, "Error on line %d, expected } or ,\n", linenumber_);
               return TokenType::kError;
             }
             break;
@@ -364,6 +365,7 @@
               ConsumeWhitespace();
               state_ = State::kExpectArrayEnd;
             } else {
+              fprintf(stderr, "Error on line %d, expected ] or ,\n", linenumber_);
               return TokenType::kError;
             }
             break;
@@ -393,6 +395,7 @@
           ConsumeWhitespace();
           state_ = State::kExpectObjectEnd;
         } else {
+          fprintf(stderr, "Error on line %d, expected , or }\n", linenumber_);
           return TokenType::kError;
         }
       } else if (object_type_.back() == ObjectType::kArray) {
@@ -405,6 +408,7 @@
           ConsumeWhitespace();
           state_ = State::kExpectArrayEnd;
         } else {
+          fprintf(stderr, "Error on line %d, expected , or ]\n", linenumber_);
           return TokenType::kError;
         }
       }