diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index dfad319..3b89e5c 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -219,7 +219,9 @@
             self.assertIsInstance(r, str)
             eq(r, expected)
         def float_eq(actual, expected):
-            self.assertAlmostEqual(float(actual), float(expected))
+            expected = float(expected)
+            self.assertAlmostEqual(float(actual), expected,
+                                   delta=abs(expected) * 1e-10)
         def nan_eq(actual, expected):
             actual = float(actual)
             self.assertNotEqual(actual, actual)