diff --git a/wakatime/constants.py b/wakatime/constants.py
index 135039e..9db227f 100644
--- a/wakatime/constants.py
+++ b/wakatime/constants.py
@@ -14,3 +14,4 @@ SUCCESS = 0
 API_ERROR = 102
 CONFIG_FILE_PARSE_ERROR = 103
 AUTH_ERROR = 104
+UNKNOWN_ERROR = 105
diff --git a/wakatime/main.py b/wakatime/main.py
index 6de441f..8e91bff 100644
--- a/wakatime/main.py
+++ b/wakatime/main.py
@@ -36,6 +36,7 @@ from .constants import (
     AUTH_ERROR,
     CONFIG_FILE_PARSE_ERROR,
     SUCCESS,
+    UNKNOWN_ERROR,
 )
 from .logger import setup_logging
 from .offlinequeue import Queue
@@ -356,7 +357,7 @@ def send_heartbeat(project=None, branch=None, hostname=None, stats={}, key=None,
     except:
         tz = None
     if tz:
-        headers['TimeZone'] = u(tz.zone)
+        headers['TimeZone'] = u(tz.zone).encode('utf-8')
 
     session_cache = SessionCache()
     session = session_cache.get()
@@ -499,3 +500,4 @@ def execute(argv=None):
             return SUCCESS
     except:
         log.traceback()
+        return UNKNOWN_ERROR