diff --git a/datemath/helpers.py b/datemath/helpers.py
index d16192b..de1616d 100644
--- a/datemath/helpers.py
+++ b/datemath/helpers.py
@@ -195,11 +195,14 @@ def evaluate(expression, now, timeZone='UTC', roundDown=True):
 
             try:
                 m = re.match('(\d*[.]?\d+)[\w+-/]', expression[i+1:])
-                num = m.group(1)
-                val = val * 10 + float(num)
-                i = i + len(num)
+                if m:
+                    num = m.group(1)
+                    val = val * 10 + float(num)
+                    i = i + len(num)
+                else:
+                    raise DateMathException('''Unable to determine a proper time qualifier.  Do you have a proper numerical number followed by a valid time unit? i.e. '+1d', '-3d/d', etc.''')
             except Exception as e:
-                raise DateMathException("Invalid numerical datematch: What I got was - match: {0}, expression: {1}, error: {2}".format(expression[i+1:], expression, e)) 
+                raise DateMathException("Invalid datematch: What I got was - re.match: {0}, expression: {1}, error: {2}".format(expression[i+1:], expression, e)) 
     
             if char == '+':
                 val = float(val)
@@ -207,6 +210,8 @@ def evaluate(expression, now, timeZone='UTC', roundDown=True):
                 val = float(-val)
         elif re.match('[a-zA-Z]+', char):
             now = calculate(now, val, unitMap(char))
+        else:
+            raise DateMathException(''''{}' is not a valid timeunit for expression: '{}' '''.format(char, expression))
         
         i += 1
     if debug: print("Fin: {0}".format(now))
diff --git a/tests.py b/tests.py
index 9dfd1c3..48f77ce 100644
--- a/tests.py
+++ b/tests.py
@@ -1,8 +1,12 @@
+# !/usr/bin/python
+# coding=utf-8
+
+
 import unittest2 as unittest
 import arrow
 from datetime import datetime as pydatetime
-from datemath import dm 
-from datemath import datemath
+from datemath import dm, datemath
+from datemath.helpers import DateMathException as DateMathException
 from dateutil import tz
 
 iso8601 = 'YYYY-MM-DDTHH:mm:ssZZ'
@@ -124,6 +128,20 @@ def testParse(self):
         self.assertEqual(dm('now-2.5d').format(iso8601), arrow.utcnow().shift(days=-2.5).format(iso8601))
 
 
+        # Catch invalid timeunits
+        self.assertRaises(DateMathException, dm, '+1,')
+        self.assertRaises(DateMathException, dm, '+1.')
+        self.assertRaises(DateMathException, dm, '+1ö')
+        self.assertRaises(DateMathException, dm, '+1ä')
+        self.assertRaises(DateMathException, dm, '+1ü')
+        self.assertRaises(DateMathException, dm, '+1ß')
+
+        try:
+            dm('+1,')
+        except DateMathException as e:
+            self.assertTrue('is not a valid timeunit' in str(e))
+
+
 if __name__ == "__main__":
     unittest.main()