diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 2b269cc..31bceb3 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -344,7 +344,8 @@
         # If the following fails either
         # the contains operator does not propagate UnicodeErrors or
         # someone has changed the default encoding
-        self.assertRaises(UnicodeError, 'g\xe2teau'.__contains__, u'\xe2')
+        self.assertRaises(UnicodeDecodeError, 'g\xe2teau'.__contains__, u'\xe2')
+        self.assertRaises(UnicodeDecodeError, u'g\xe2teau'.__contains__, '\xe2')
 
         self.assertTrue(u'' in '')
         self.assertTrue('' in u'')
@@ -375,6 +376,7 @@
         self.assertTrue(u'asdf' not in u'')
 
         self.assertRaises(TypeError, u"abc".__contains__)
+        self.assertRaises(TypeError, u"abc".__contains__, object())
 
     def test_formatting(self):
         string_tests.MixinStrUnicodeUserStringTest.test_formatting(self)
diff --git a/Misc/NEWS b/Misc/NEWS
index cfdf975..08369a2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #1680159: unicode coercion during an 'in' operation no longer masks
+  the underlying error when the coercion fails for the left hand operand.
+
 - Issue #7491: Metaclass's __cmp__ method was ignored.
 
 - Issue #7466: segmentation fault when the garbage collector is called
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e85b20f..79e824e 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6502,8 +6502,6 @@
     /* Coerce the two arguments */
     sub = PyUnicode_FromObject(element);
     if (!sub) {
-        PyErr_SetString(PyExc_TypeError,
-                        "'in <string>' requires string as left operand");
         return -1;
     }