--- a/markup/builder.py
+++ b/markup/builder.py
@@ -11,7 +11,7 @@
 # individuals. For the exact contribution history, see the revision
 # history and logs, available at http://markup.edgewall.org/log/.
 
-from markup.core import Attributes, Namespace, QName, Stream
+from markup.core import Attributes, Namespace, QName, Stream, escape
 
 __all__ = ['Fragment', 'Element', 'tag']
 
@@ -34,7 +34,7 @@
         return self
 
     def __iter__(self):
-        return iter(self.generate())
+        return self._generate()
 
     def __repr__(self):
         return '<%s>' % self.__class__.__name__
@@ -169,14 +169,20 @@
             if value is None:
                 continue
             attr = attr.rstrip('_').replace('_', '-')
-            self.attrib.set(attr, value)
-        return Fragment.__call__(self, *args)
+            self.attrib.set(attr, escape(value))
+        Fragment.__call__(self, *args)
+        return self
 
     def __repr__(self):
         return '<%s "%s">' % (self.__class__.__name__, self.tag)
 
     def _generate(self):
-        yield Stream.START, (self.tag, self.attrib), (None, -1, -1)
+        attrib = Attributes()
+        for attr, value in self.attrib:
+            if not isinstance(value, basestring):
+                value = unicode(value)
+            attrib.append((attr, value))
+        yield Stream.START, (self.tag, attrib), (None, -1, -1)
         for kind, data, pos in Fragment._generate(self):
             yield kind, data, pos
         yield Stream.END, self.tag, (None, -1, -1)

--- a/markup/eval.py
+++ b/markup/eval.py
@@ -199,6 +199,7 @@
         node.expr = self.visit(node.expr, *args, **kwargs)
         return node
     visitUnaryAdd = visitUnarySub = visitNot = visitInvert = _visitUnaryOp
+    visitBackquote = _visitUnaryOp
 
     # Identifiers, Literals and Comprehensions
 

--- a/markup/tests/builder.py
+++ b/markup/tests/builder.py
@@ -29,6 +29,16 @@
         self.assertEqual((Stream.TEXT, u'Bar', (None, -1, -1)), bits.next())
         self.assertEqual((Stream.END, 'a', (None, -1, -1)), bits.next())
 
+    def test_nonstring_attributes(self):
+        """
+        Verify that if an attribute value is given as an int (or some other
+        non-string type), it is coverted to a string when the stream is
+        generated.
+        """
+        event = iter(tag.foo(id=3)).next()
+        self.assertEqual((Stream.START, ('foo', [('id', '3')]), (None, -1, -1)),
+                         event)
+
 
 def suite():
     suite = unittest.TestSuite()