diff --git a/pronterface.py b/pronterface.py
index 336155f..b553e3f 100755
--- a/pronterface.py
+++ b/pronterface.py
@@ -49,7 +49,10 @@ def dosify(name):
     return os.path.split(name)[1].split(".")[0][:8]+".g"
 
 def parse_temperature_report(report, key):
-    return float(filter(lambda x: x.startswith(key), report.split())[0].split(":")[1].split("/")[0])
+    if key in report:
+        return float(filter(lambda x: x.startswith(key), report.split())[0].split(":")[1].split("/")[0])
+    else: 
+        return -1.0
 
 def format_time(timestamp):
     return datetime.datetime.fromtimestamp(timestamp).strftime("%H:%M:%S")