diff --git a/common/lib/calc/calc.py b/common/lib/calc/calc.py
index 2f33b66bfd..2ee82e2fb4 100644
--- a/common/lib/calc/calc.py
+++ b/common/lib/calc/calc.py
@@ -182,8 +182,8 @@ def evaluator(variables, functions, string, cs=False):
 
     number_part = Word(nums)
 
-    # 0.33 or 7 or .34
-    inner_number = (number_part + Optional("." + number_part)) | ("." + number_part)
+    # 0.33 or 7 or .34 or 16.
+    inner_number = (number_part + Optional("." + Optional(number_part))) | ("." + number_part)
 
     # 0.33k or -17
     number = (Optional(minus | plus) + inner_number
diff --git a/common/lib/calc/tests/test_calc.py b/common/lib/calc/tests/test_calc.py
index 58d0860af6..cfa1b7525d 100644
--- a/common/lib/calc/tests/test_calc.py
+++ b/common/lib/calc/tests/test_calc.py
@@ -5,6 +5,7 @@ Unit tests for calc.py
 import unittest
 import numpy
 import calc
+from pyparsing import ParseException
 
 
 class EvaluatorTest(unittest.TestCase):
@@ -20,6 +21,11 @@ class EvaluatorTest(unittest.TestCase):
     def test_number_input(self):
         """
         Test different kinds of float inputs
+
+        See also
+          test_trailing_period (slightly different)
+          test_exponential_answer
+          test_si_suffix
         """
         easy_eval = lambda x: calc.evaluator({}, {}, x)
 
@@ -30,7 +36,22 @@ class EvaluatorTest(unittest.TestCase):
         self.assertEqual(easy_eval("-13"), -13)
         self.assertEqual(easy_eval("-3.14"), -3.14)
         self.assertEqual(easy_eval("-.618033989"), -0.618033989)
-        # See also test_exponential_answer and test_si_suffix
+
+    def test_period(self):
+        """
+        The string '.' should not evaluate to anything.
+        """
+        self.assertRaises(ParseException, calc.evaluator, {}, {}, '.')
+        self.assertRaises(ParseException, calc.evaluator, {}, {}, '1+.')
+
+    def test_trailing_period(self):
+        """
+        Test that things like '4.' will be 4 and not throw an error
+        """
+        try:
+            self.assertEqual(4.0, calc.evaluator({}, {}, '4.'))
+        except ParseException:
+            self.fail("'4.' is a valid input, but threw an exception")
 
     def test_exponential_answer(self):
         """