diff --git a/pipenv/patched/prettytoml/elements/abstracttable.py b/pipenv/patched/prettytoml/elements/abstracttable.py
index 59fd5748..48663aed 100644
--- a/pipenv/patched/prettytoml/elements/abstracttable.py
+++ b/pipenv/patched/prettytoml/elements/abstracttable.py
@@ -1,8 +1,13 @@
+try:
+    from collections.abc import Mapping
+except ImportError:
+    from collections import Mapping
+
 from prettytoml.elements.common import ContainerElement
 from prettytoml.elements import traversal
 
 
-class AbstractTable(ContainerElement, traversal.TraversalMixin):
+class AbstractTable(ContainerElement, traversal.TraversalMixin, Mapping):
     """
     Common code for handling tables as key-value pairs with metadata elements sprinkled all over.
 
@@ -37,6 +42,9 @@ class AbstractTable(ContainerElement, traversal.TraversalMixin):
     def __len__(self):
         return len(tuple(self._enumerate_items()))
 
+    def __iter__(self):
+        return (key for key, _ in self.items())
+
     def __contains__(self, item):
         return item in self.keys()
 
diff --git a/pipenv/utils.py b/pipenv/utils.py
index 8094b175..4bd894a0 100644
--- a/pipenv/utils.py
+++ b/pipenv/utils.py
@@ -47,7 +47,6 @@ from contextlib import contextmanager
 from .pep508checker import lookup
 from .environments import PIPENV_MAX_ROUNDS, PIPENV_CACHE_DIR
 
-from prettytoml.elements.abstracttable import AbstractTable
 try:
     from collections.abc import Mapping
 except ImportError:
@@ -646,7 +645,7 @@ def is_star(val):
 
 
 def is_pinned(val):
-    if isinstance(val, Mapping) or isinstance(val, AbstractTable):
+    if isinstance(val, Mapping):
         val = val.get('version')
     return isinstance(val, six.string_types) and val.startswith('==')
 
diff --git a/tasks/vendoring/patches/patched/prettytoml-table-iter.patch b/tasks/vendoring/patches/patched/prettytoml-table-iter.patch
new file mode 100644
index 00000000..5758e122
--- /dev/null
+++ b/tasks/vendoring/patches/patched/prettytoml-table-iter.patch
@@ -0,0 +1,28 @@
+diff --git a/pipenv/patched/prettytoml/elements/abstracttable.py b/pipenv/patched/prettytoml/elements/abstracttable.py
+index 59fd5748..48663aed 100644
+--- a/pipenv/patched/prettytoml/elements/abstracttable.py
++++ b/pipenv/patched/prettytoml/elements/abstracttable.py
+@@ -1,8 +1,13 @@
++try:
++    from collections.abc import Mapping
++except ImportError:
++    from collections import Mapping
++
+ from prettytoml.elements.common import ContainerElement
+ from prettytoml.elements import traversal
+
+
+-class AbstractTable(ContainerElement, traversal.TraversalMixin):
++class AbstractTable(ContainerElement, traversal.TraversalMixin, Mapping):
+     """
+     Common code for handling tables as key-value pairs with metadata elements sprinkled all over.
+
+@@ -37,6 +42,9 @@ class AbstractTable(ContainerElement, traversal.TraversalMixin):
+     def __len__(self):
+         return len(tuple(self._enumerate_items()))
+
++    def __iter__(self):
++        return (key for key, _ in self.items())
++
+     def __contains__(self, item):
+         return item in self.keys()