diff --git a/pywait.py b/pywait.py
index c5c67c2..5cd02ad 100644
--- a/pywait.py
+++ b/pywait.py
@@ -26,9 +26,10 @@ def valid_connection_spec(connection_spec):
 
     if spec_parts[0] not in valid_protocol_specs:
         raise ValueError('Invalid spec. Protocol should any of ' + ' '.join(valid_protocol_specs))
-
-    if int(spec_parts[2]) > 65535:
-        raise ValueError('Invalid port spec.')
+    
+    spec_port = int(spec_parts[2])
+    if spec_port > 65535 or spec_port < 1:
+        raise ValueError('Invalid port spec (greater/lower than allowed).')
 
     return tuple(spec_parts)