diff -r 2c70897e5f98 Tools/clinic/clinic.py
--- a/Tools/clinic/clinic.py	Fri Aug 01 21:57:49 2014 +0100
+++ b/Tools/clinic/clinic.py	Sat Aug 02 02:12:36 2014 +0200
@@ -2858,7 +2858,7 @@ class bool_return_converter(CReturnConve
 
     def render(self, function, data):
         self.declare(data)
-        self.err_occurred_if("_return_value == -1", data)
+        self.err_occurred_if("_return_value == (%s)-1" % self.type, data)
         data.return_conversion.append('return_value = PyBool_FromLong((long)_return_value);\n')
 
 class long_return_converter(CReturnConverter):
@@ -2868,7 +2868,7 @@ class long_return_converter(CReturnConve
 
     def render(self, function, data):
         self.declare(data)
-        self.err_occurred_if("_return_value == -1", data)
+        self.err_occurred_if("_return_value == (%s)-1" % self.type, data)
         data.return_conversion.append(
             ''.join(('return_value = ', self.conversion_fn, '(', self.cast, '_return_value);\n')))