diff --git a/openstack_requirements/cmds/edit_constraint.py b/openstack_requirements/cmds/edit_constraint.py
index 1fea91aee0..e1bb602449 100644
--- a/openstack_requirements/cmds/edit_constraint.py
+++ b/openstack_requirements/cmds/edit_constraint.py
@@ -21,10 +21,11 @@ from openstack_requirements import requirement
 
 
 def edit(reqs, name, replacement):
+    key = requirement.canonical_name(name)
     if not replacement:
-        reqs.pop(name, None)
+        reqs.pop(key, None)
     else:
-        reqs[name] = [
+        reqs[key] = [
             (requirement.Requirement('', '', '', '', replacement), '')]
     result = []
     for entries in reqs.values():
diff --git a/openstack_requirements/requirement.py b/openstack_requirements/requirement.py
index bf568804bc..e8b3b688fb 100644
--- a/openstack_requirements/requirement.py
+++ b/openstack_requirements/requirement.py
@@ -41,6 +41,11 @@ url_re = re.compile(
     '#egg=(?P<name>[-\.\w]+)')
 
 
+def canonical_name(req_name):
+    """Return the canonical form of req_name."""
+    return pkg_resources.safe_name(req_name).lower()
+
+
 def parse(content, permit_urls=False):
     return to_dict(to_reqs(content, permit_urls=permit_urls))
 
@@ -134,7 +139,8 @@ def to_dict(req_sequence):
     reqs = dict()
     for req, req_line in req_sequence:
         if req is not None:
-            reqs.setdefault(req.package.lower(), []).append((req, req_line))
+            key = canonical_name(req.package)
+            reqs.setdefault(key, []).append((req, req_line))
     return reqs
 
 
diff --git a/openstack_requirements/tests/test_edit_constraint.py b/openstack_requirements/tests/test_edit_constraint.py
index 9bad8e6db8..0c86ddb76f 100644
--- a/openstack_requirements/tests/test_edit_constraint.py
+++ b/openstack_requirements/tests/test_edit_constraint.py
@@ -83,3 +83,10 @@ class TestEdit(testtools.TestCase):
         res = edit.edit(reqs, 'foo', 'foo==1.3')
         self.assertEqual(requirement.Requirements(
             [requirement.Requirement('', '', '', '', 'foo==1.3')]), res)
+
+    def test_replace_non_canonical(self):
+        new_req = '-e file:///path#egg=foo_baz'
+        reqs = requirement.parse("foo-baz===1.0.2\n")
+        res = edit.edit(reqs, 'foo_baz', new_req)
+        self.assertEqual(res, requirement.Requirements(
+            [requirement.Requirement('', '', '', '', new_req)]))
diff --git a/openstack_requirements/tests/test_requirement.py b/openstack_requirements/tests/test_requirement.py
index 23441023b9..defdce65d6 100644
--- a/openstack_requirements/tests/test_requirement.py
+++ b/openstack_requirements/tests/test_requirement.py
@@ -148,3 +148,17 @@ class TestToReqs(testtools.TestCase):
             set(['oslo.config', 'oslo.concurrency', 'oslo.context']),
             set(reqs.keys()),
         )
+
+
+class TestCanonicalName(testtools.TestCase):
+
+    def test_underscores(self):
+        self.assertEqual('foo-bar', requirement.canonical_name('Foo_bar'))
+
+
+class TestToDict(testtools.TestCase):
+
+    def test_canonicalises(self):
+        req = requirement.Requirement('Foo_bar', '', '', '', '')
+        self.assertEqual(
+            {'foo-bar': [(req, '')]}, requirement.to_dict([(req, '')]))