diff --git a/pyhamtools/callinfo.py b/pyhamtools/callinfo.py
index efa73fa..f20d1a2 100644
--- a/pyhamtools/callinfo.py
+++ b/pyhamtools/callinfo.py
@@ -214,7 +214,10 @@ class Callinfo(object):
                 pfx = re.sub('/', '', pfx.group(0))
                 #make sure that the remaining part is actually a callsign (avoid: OZ/JO81)
                 rest = re.search('/[A-Z0-9]+', entire_callsign)
-                rest = re.sub('/', '', rest.group(0))
+                if rest is None:
+                    self._logger.warning("non latin characters in callsign '{0}'".format(entire_callsign))
+                    raise KeyError
+                rest = re.sub('/', '', rest.group(0))  
                 if re.match('^[\\d]{0,1}[A-Z]{1,2}\\d([A-Z]{1,4}|\\d{3,3}|\\d{1,3}[A-Z])[A-Z]{0,5}$', rest):
                     return self._iterate_prefix(pfx)
 
diff --git a/test/test_callinfo.py b/test/test_callinfo.py
index 5146449..8500188 100644
--- a/test/test_callinfo.py
+++ b/test/test_callinfo.py
@@ -265,6 +265,15 @@ class Test_callinfo_methods:
                 fix_callinfo._dismantle_callsign("OZ/JO85")
 
 
+    def test_dismantle_callsign_with_cyrillic_characters(self, fix_callinfo):
+
+        with pytest.raises(KeyError):
+            fix_callinfo._dismantle_callsign("RД3MAS") #cyrillic letter 'Д' in call
+        with pytest.raises(KeyError):
+            fix_callinfo._dismantle_callsign("RД3/K9MAS") #cyrillic letter 'Д' in prefix
+        with pytest.raises(KeyError):
+            fix_callinfo._dismantle_callsign("R2EA/М") #cyrillic letter 'M' in appendix
+
     def test_dismantle_callsign_with_VK9_special_suffixes(self, fix_callinfo):
 
         if fix_callinfo._lookuplib._lookuptype == "clublog":