diff --git a/README.md b/README.md
index 2e956d2..fd4f4e1 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,9 @@
-# ejabberd-metrics
+## ejabberd-tools
 
+### error codes
+Lookup table for all custom error codes.
+The potential reasons are sorted by probability of being the root cause.
+
+| code | potential reason |
+| :---: | :---|
+| 17 | login credential mismatch, potential api permission problem |
diff --git a/api.py b/api.py
index ccd63e4..7807390 100644
--- a/api.py
+++ b/api.py
@@ -35,7 +35,11 @@ class EjabberdApi:
             status = self.cmd('status', {})
 
             # matches
-            tmp = ver_str.findall(status)[0]
+            try:
+                tmp = ver_str.findall(status)[0]
+            # raise SystemExit code 17 if no status message is received
+            except TypeError:
+                raise SystemExit(17)
 
             # return parsed version string
             return version.parse(tmp)