diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 699c621..d86298d 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -12,7 +12,11 @@
 
     def ftest(self, name, value, expected):
         if abs(value-expected) > eps:
-            self.fail('%s returned %f, expected %f'%\
+            # Use %r instead of %f so the error message
+            # displays full precision. Otherwise discrepancies
+            # in the last few bits will lead to very confusing
+            # error messages
+            self.fail('%s returned %r, expected %r' %
                       (name, value, expected))
 
     def testConstants(self):