diff --git a/Lib/fontTools/feaLib/parser.py b/Lib/fontTools/feaLib/parser.py
index 7902773f2..bb33006ae 100644
--- a/Lib/fontTools/feaLib/parser.py
+++ b/Lib/fontTools/feaLib/parser.py
@@ -340,6 +340,14 @@ class Parser(object):
                 self.expect_symbol_("'")
                 hasMarks = marked = True
             if marked:
+                if suffix:
+                    # makeotf also reports this as an error, while FontForge
+                    # silently inserts ' in all the intervening glyphs.
+                    # https://github.com/fonttools/fonttools/pull/1096
+                    raise FeatureLibError(
+                        "Unsupported contextual target sequence: at most "
+                        "one run of marked (') glyph/class names allowed",
+                        self.cur_token_location_)
                 glyphs.append(gc)
             elif glyphs:
                 suffix.append(gc)
diff --git a/Tests/feaLib/parser_test.py b/Tests/feaLib/parser_test.py
index 54814dc4d..614986525 100644
--- a/Tests/feaLib/parser_test.py
+++ b/Tests/feaLib/parser_test.py
@@ -1220,6 +1220,42 @@ class ParserTest(unittest.TestCase):
         self.assertEqual(sub.glyph, "f_f_i")
         self.assertEqual(sub.replacement, ("f", "f", "i"))
 
+    def test_split_marked_glyphs_runs(self):
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Unsupported contextual target sequence",
+            self.parse, "feature test{"
+                        "    ignore pos a' x x A';"
+                        "} test;")
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Unsupported contextual target sequence",
+            self.parse, "lookup shift {"
+                        "    pos a <0 -10 0 0>;"
+                        "    pos A <0 10 0 0>;"
+                        "} shift;"
+                        "feature test {"
+                        "    sub a' lookup shift x x A' lookup shift;"
+                        "} test;")
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Unsupported contextual target sequence",
+            self.parse, "feature test {"
+                        "    ignore sub a' x x A';"
+                        "} test;")
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Unsupported contextual target sequence",
+            self.parse, "lookup upper {"
+                        "    sub a by A;"
+                        "} upper;"
+                        "lookup lower {"
+                        "    sub A by a;"
+                        "} lower;"
+                        "feature test {"
+                        "    sub a' lookup upper x x A' lookup lower;"
+                        "} test;")
+
     def test_substitute_from(self):  # GSUB LookupType 3
         doc = self.parse("feature test {"
                          "  substitute a from [a.1 a.2 a.3];"
diff --git a/tox.ini b/tox.ini
index 4966d8bf4..9beff2542 100644
--- a/tox.ini
+++ b/tox.ini
@@ -23,7 +23,7 @@ commands =
     nocov: pytest {posargs}
 
 [testenv:htmlcov]
-basepython = {env:TOXPYTHON:python3.5}
+basepython = {env:TOXPYTHON:python3.6}
 deps =
     coverage>=4.3
 skip_install = true
@@ -44,7 +44,7 @@ commands =
     codecov --env TOXENV
 
 [testenv:bdist]
-basepython = {env:TOXPYTHON:python3.5}
+basepython = {env:TOXPYTHON:python3.6}
 deps =
     setuptools
     wheel