diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index ba1497f..f4773ae 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -13,6 +13,8 @@ This project adheres to `Semantic Versioning`_.
 - Issue in which explicitly specified NIC names were being overwritten by
   names auto-derived from network names when attempting to set both NIC name
   and network names in a single ``cot edit-hardware`` call.
+- ``cot edit-properties`` again accepts property values containing the characters
+  ``+`` and ``=`` (`#59`_).
 
 **Added**
 
@@ -593,6 +595,7 @@ Initial public release.
 .. _#53: https://github.com/glennmatthews/cot/issues/53
 .. _#54: https://github.com/glennmatthews/cot/issues/54
 .. _#58: https://github.com/glennmatthews/cot/issues/58
+.. _#59: https://github.com/glennmatthews/cot/issues/59
 
 .. _Semantic Versioning: http://semver.org/
 .. _`PEP 8`: https://www.python.org/dev/peps/pep-0008/
diff --git a/COT/edit_properties.py b/COT/edit_properties.py
index d9106af..5648491 100644
--- a/COT/edit_properties.py
+++ b/COT/edit_properties.py
@@ -3,7 +3,7 @@
 # edit_properties.py - Implements "edit-properties" sub-command
 #
 # August 2013, Glenn F. Matthews
-# Copyright (c) 2013-2016 the COT project developers.
+# Copyright (c) 2013-2017 the COT project developers.
 # See the COPYRIGHT.txt file at the top-level directory of this distribution
 # and at https://github.com/glennmatthews/cot/blob/master/COPYRIGHT.txt.
 #
@@ -88,14 +88,57 @@ def config_file(self, value):
 
     @property
     def properties(self):
-        """List of property (key, value, type) tuples to update."""
+        """List of property (key, value, type) tuples to update.
+
+        Properties may also be set from strings (such as by CLI)
+        with the syntax ``<key>[=<value>][+<type>]``.
+
+        Examples:
+          ::
+
+            >>> from COT.ui_shared import UI
+            >>> i = COTEditProperties(UI())
+            >>> i.properties
+            []
+            >>> i.properties = [
+            ... "no_value",
+            ... "key=value",
+            ... "string_type+string",
+            ... "full-type=yes+boolean",
+            ... ]
+            >>> print("\\n".join(["{0:15} {1:10} {2}".format(*p)
+            ... for p in i.properties]))
+            no_value        None       None
+            key             value      None
+            string_type     None       string
+            full-type       yes        boolean
+            >>> i.properties = [
+            ... "ssh=autopubkey=ssh-rsa AA...q+t0...Tuw== root@MASTER",
+            ... "tricky=+foo",
+            ... "tricky_value=++foo==++",
+            ... "trickiest=bar+foo=hello+boolean",
+            ... ]
+            >>> print("\\n".join([str(p) for p in i.properties]))
+            ('ssh', 'autopubkey=ssh-rsa AA...q+t0...Tuw== root@MASTER', None)
+            ('tricky', '', 'foo')
+            ('tricky_value', '++foo==++', None)
+            ('trickiest', 'bar+foo=hello', 'boolean')
+        """
         return self._properties
 
     @properties.setter
     def properties(self, value):
         new_value = []
         for prop in value:
-            match = re.match(r"^([^=+]+?)(=[^=+]*?)?(\+[^=+]*?)?$", prop)
+            # While our string is delimited by '+' and '=' as "key=value+type",
+            # those characters may also be included in the actual value,
+            # as in an SSH private key:
+            # 'autopubkey=ssh-rsa AA...gl/p...q+t0...Tuw== root@MASTER'
+            # or other base64-encoded value ([A-Za-z0-9+/=] or [A-Za-z0-9-_=])
+            # So we have to be "clever" in how we parse things.
+            # To handle ambiguity, we presume that the characters '+' and '='
+            # MAY appear in a value string but NOT in a key or prop_type.
+            match = re.match(r"^([^=+]+)(=.*?)?(\+[^=+]+?)?$", prop)
             if not match:
                 raise InvalidInputError("Invalid property '{0}' - properties "
                                         "must be in 'key[=value][+type]' form"
@@ -113,7 +156,7 @@ def properties(self, value):
 
     @property
     def transports(self):
-        """Transport mechanism(s) for environment properties.."""
+        """Transport mechanism(s) for environment properties."""
         return self._transports
 
     _KNOWN_TRANSPORTS = {
diff --git a/COT/tests/test_doctests.py b/COT/tests/test_doctests.py
index 81fe9e2..2265bad 100644
--- a/COT/tests/test_doctests.py
+++ b/COT/tests/test_doctests.py
@@ -3,7 +3,7 @@
 # test_doctests.py - test runner for COT doctests
 #
 # July 2016, Glenn F. Matthews
-# Copyright (c) 2016 the COT project developers.
+# Copyright (c) 2016-2017 the COT project developers.
 # See the COPYRIGHT.txt file at the top-level directory of this distribution
 # and at https://github.com/glennmatthews/cot/blob/master/COPYRIGHT.txt.
 #
@@ -29,5 +29,6 @@ def load_tests(*_):
     suite.addTests(DocTestSuite('COT.cli'))
     suite.addTests(DocTestSuite('COT.deploy'))
     suite.addTests(DocTestSuite('COT.edit_hardware'))
+    suite.addTests(DocTestSuite('COT.edit_properties'))
     suite.addTests(DocTestSuite('COT.file_reference'))
     return suite