diff --git a/taskflow/patterns/linear_flow.py b/taskflow/patterns/linear_flow.py
index 650d93fd..9f85efe9 100644
--- a/taskflow/patterns/linear_flow.py
+++ b/taskflow/patterns/linear_flow.py
@@ -40,6 +40,7 @@ class Flow(flow.Flow):
         # NOTE(imelnikov): we add item to the end of flow, so it should
         # not provide anything previous items of the flow require
         requires = self.requires
+        provides = self.provides
         for item in items:
             requires |= item.requires
             out_of_order = requires & item.provides
@@ -49,6 +50,15 @@ class Flow(flow.Flow):
                     "by previous item(s) of linear flow %(flow)s"
                     % dict(item=item.name, flow=self.name,
                            oo=sorted(out_of_order)))
+            same_provides = provides & item.provides
+            if same_provides:
+                raise exceptions.DependencyFailure(
+                    "%(item)s provides %(value)s but is already being"
+                    " provided by %(flow)s and duplicate producers"
+                    " are disallowed"
+                    % dict(item=item.name, flow=self.name,
+                           value=sorted(same_provides)))
+            provides |= item.provides
 
         self._children.extend(items)
         return self
diff --git a/taskflow/patterns/unordered_flow.py b/taskflow/patterns/unordered_flow.py
index 294176e6..200fbdd0 100644
--- a/taskflow/patterns/unordered_flow.py
+++ b/taskflow/patterns/unordered_flow.py
@@ -52,7 +52,15 @@ class Flow(flow.Flow):
                     "by other item(s) of unordered flow %(flow)s"
                     % dict(item=item.name, flow=self.name,
                            oo=sorted(bad_provs)))
-            provides |= item_provides
+            same_provides = provides & item.provides
+            if same_provides:
+                raise exceptions.DependencyFailure(
+                    "%(item)s provides %(value)s but is already being"
+                    " provided by %(flow)s and duplicate producers"
+                    " are disallowed"
+                    % dict(item=item.name, flow=self.name,
+                           value=sorted(same_provides)))
+            provides |= item.provides
 
         for item in items:
             bad_reqs = provides & item.requires
diff --git a/taskflow/tests/unit/test_flow_dependencies.py b/taskflow/tests/unit/test_flow_dependencies.py
index 0bdb7abf..cf2f8f9a 100644
--- a/taskflow/tests/unit/test_flow_dependencies.py
+++ b/taskflow/tests/unit/test_flow_dependencies.py
@@ -110,12 +110,25 @@ class FlowDependenciesTest(test.TestCase):
         self.assertEqual(flow.provides, set(['x', 'y', 'q', 'i', 'j', 'k']))
 
     def test_linear_flow_self_requires(self):
-        flow = lf.Flow('uf')
+        flow = lf.Flow('lf')
         self.assertRaises(exceptions.InvariantViolationException,
                           flow.add,
                           utils.TaskNoRequiresNoReturns(rebind=['x'],
                                                         provides='x'))
 
+    def test_linear_flow_provides_same_values(self):
+        flow = lf.Flow('lf').add(utils.TaskOneReturn(provides='x'))
+        self.assertRaises(exceptions.DependencyFailure,
+                          flow.add,
+                          utils.TaskOneReturn(provides='x'))
+
+    def test_linear_flow_provides_same_values_one_add(self):
+        flow = lf.Flow('lf')
+        self.assertRaises(exceptions.DependencyFailure,
+                          flow.add,
+                          utils.TaskOneReturn(provides='x'),
+                          utils.TaskOneReturn(provides='x'))
+
     def test_unordered_flow_without_dependencies(self):
         flow = uf.Flow('uf').add(
             utils.TaskNoRequiresNoReturns('task1'),
@@ -182,6 +195,19 @@ class FlowDependenciesTest(test.TestCase):
         self.assertEqual(flow.requires, set(['a', 'b', 'c', 'x', 'y', 'z']))
         self.assertEqual(flow.provides, set(['d', 'e', 'f', 'i', 'j', 'k']))
 
+    def test_unordered_flow_provides_same_values(self):
+        flow = uf.Flow('uf').add(utils.TaskOneReturn(provides='x'))
+        self.assertRaises(exceptions.DependencyFailure,
+                          flow.add,
+                          utils.TaskOneReturn(provides='x'))
+
+    def test_unordered_flow_provides_same_values_one_add(self):
+        flow = uf.Flow('uf')
+        self.assertRaises(exceptions.DependencyFailure,
+                          flow.add,
+                          utils.TaskOneReturn(provides='x'),
+                          utils.TaskOneReturn(provides='x'))
+
     def test_nested_flows_requirements(self):
         flow = uf.Flow('uf').add(
             lf.Flow('lf').add(
@@ -196,6 +222,13 @@ class FlowDependenciesTest(test.TestCase):
         self.assertEqual(flow.requires, set(['a', 'b', 'c']))
         self.assertEqual(flow.provides, set(['x', 'y', 'z', 'q']))
 
+    def test_nested_flows_provides_same_values(self):
+        flow = lf.Flow('lf').add(
+            uf.Flow('uf').add(utils.TaskOneReturn(provides='x')))
+        self.assertRaises(exceptions.DependencyFailure,
+                          flow.add,
+                          gf.Flow('gf').add(utils.TaskOneReturn(provides='x')))
+
     def test_graph_flow_without_dependencies(self):
         flow = gf.Flow('gf').add(
             utils.TaskNoRequiresNoReturns('task1'),