diff --git a/.travis.yml b/.travis.yml
index 2512c9a..e088560 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,28 +1,52 @@
 language: python
 sudo: required
-dist: trusty
-python:
- - "2.7"
+jobs:
+  include:
+    - name: "python 2.7 qt4 trusty pgmpl"
+      dist: trusty
+      python: 2.7
+#      virtualenv:
+#        system_site_packages: true
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get -y install python-qt4
+      before_script:
+       # From pyqtgraph's .travis.yml: https://github.com/pyqtgraph/pyqtgraph/blob/develop/.travis.yml
+       # We need to create a (fake) display on Travis, let's use a funny resolution
+       - export DISPLAY=:99.0
+       - "sh -e /etc/init.d/xvfb start"
+       - /sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1400x900x24 -ac +extension GLX +render
+       - export PGMPL_TEST_VERBOSE=1
+    - name: "python 2.7 qt5 bionic pgmpl"
+      dist: bionic
+      python: 2.7
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get -y install python-pyqt5
+      services:
+       - xvfb
+    - name: "python 3.6 qt5 bionic pgmpl"
+      dist: bionic
+      python: 3.6
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get -y install python3-pyqt5
+      services:
+       - xvfb
 
 # https://stackoverflow.com/a/35029430/6605826
-
+# system_site_packages limits py versions https://travis-ci.community/t/python-3-6-and-3-7-with-system-site-packages-enabled-fails-to-activate-on-xenial/1697
 virtualenv:
   system_site_packages: true
 
+# apt-get commands depend on py version: https://stackoverflow.com/a/20621143/6605826
 install:
- - sudo apt-get update
- - sudo apt-get -y install python-qt4
+# - sudo apt-get update
+# - if [[ $TRAVIS_PYTHON_VERSION < 3 ]]; then sudo apt-get -y install python-qt4; fi
+# - if [[ $TRAVIS_PYTHON_VERSION > 3 ]]; then sudo apt-get -y install python3-pyqt5; fi
  - pip install -r requirements.txt
  - pip install codecov coverage
 
-before_script:
- # From pyqtgraph's .travis.yml: https://github.com/pyqtgraph/pyqtgraph/blob/develop/.travis.yml
- # We need to create a (fake) display on Travis, let's use a funny resolution
- - export DISPLAY=:99.0
- - "sh -e /etc/init.d/xvfb start"
- - /sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1400x900x24 -ac +extension GLX +render
- - export PGMPL_TEST_VERBOSE=1
-
 script:
  - coverage run -m unittest discover --pattern=*.py -s tests
 
diff --git a/pgmpl/axes.py b/pgmpl/axes.py
index 6895559..e54884a 100644
--- a/pgmpl/axes.py
+++ b/pgmpl/axes.py
@@ -110,9 +110,12 @@ def _make_custom_verts(verts):
         :param verts: sequence of (x, y), optional
         :return: a pyqt path suitable for use with Axes.plot()'s symbol keyword.
         """
+        from pyqtgraph.graphicsItems.ScatterPlotItem import Symbols
         verts_x = np.array([vert[0] for vert in verts])
         verts_y = np.array([vert[1] for vert in verts])
-        return pg.arrayToQPath(verts_x, verts_y, connect='all')
+        key = 'custom_pgmpl_symbol_1'
+        Symbols[key] = pg.arrayToQPath(verts_x, verts_y, connect='all')
+        return key
 
     def scatter(self, x=None, y=None, **kwargs):
         """
@@ -171,7 +174,6 @@ def scatter(self, x=None, y=None, **kwargs):
         plotkw['symbolPen'] = [pg.mkPen(**spkw) for spkw in sympen_kw]
         if plotkw.get('symbol', None) is None:  # Shouldn't happen unless user sets None explicitly b/c default is 'o'
             plotkw['symbol'] = self._make_custom_verts(kwargs.pop('verts', None))
-
         return super(Axes, self).plot(x=x, y=y, **plotkw)
 
     def imshow(self, x=None, aspect=None, **kwargs):
@@ -190,8 +192,7 @@ def contour(self, *args, **kwargs):
     def contourf(self, *args, **kwargs):
         printd('  pgmpl.axes.Axes.contourf()...')
         kwargs['filled'] = True
-        contours = QuadContourSet(self, *args, **kwargs)
-        return contours
+        return QuadContourSet(self, *args, **kwargs)
 
     def set_xlabel(self, label):
         """Imitates basic use of matplotlib.axes.Axes.set_xlabel()"""
diff --git a/pgmpl/figure.py b/pgmpl/figure.py
index 2cc8450..c8c7cf2 100644
--- a/pgmpl/figure.py
+++ b/pgmpl/figure.py
@@ -135,6 +135,11 @@ def add_subplot(self, nrows, ncols, index, **kwargs):
         col = (index-1) % ncols
         ax = Axes(nrows=nrows, ncols=ncols, index=index, **kwargs)
         self.layout.addItem(ax, row+1, col)
+        try:
+            tolist(self.axes)
+        except RuntimeError:
+            print('Warning: Qt has deleted the axes; figure had a residual reference to a bad Qt object. (add_subplot)')
+            self.axes = None
         self.axes = ax if self.axes is None else tolist(self.axes) + [ax]
         self.fig_colspan = max([ncols, self.fig_colspan])
         self.refresh_suptitle()
@@ -196,10 +201,14 @@ def gca(self):
         Imitation of matplotlib gca()
         :return: Current axes for this figure, creating them if necessary
         """
+        if self.axes is not None:
+            try:
+                ax = list(flatten(np.atleast_1d(self.axes)))[-1]
+            except RuntimeError:  # Happens if Qt has deleted the Axes
+                print('Warning: Qt has deleted the axes; figure had a residual reference to a bad Qt object. (gca)')
+                self.axes = None
         if self.axes is None:
             ax = self.add_subplot(1, 1, 1)
-        else:
-            ax = list(flatten(np.atleast_1d(self.axes)))[-1]
         return ax
 
     def close(self):
diff --git a/pgmpl/translate.py b/pgmpl/translate.py
index bb5eae5..5cf4fd2 100644
--- a/pgmpl/translate.py
+++ b/pgmpl/translate.py
@@ -28,6 +28,17 @@
 
 # pgmpl imports
 from pgmpl.util import set_debug, printd, tolist
+from pyqtgraph.graphicsItems.ScatterPlotItem import Symbols
+
+# Install custom symbols
+theta = np.linspace(0, 2 * np.pi, 36)
+Symbols['.'] = pg.arrayToQPath(np.cos(theta) * 0.125, np.sin(theta) * 0.125, connect='all')
+Symbols[','] = pg.arrayToQPath(np.array([-0.01, 0, 0.01, 0, -0.01]), np.array([0, 0.01, 0, -0.01, 0]), connect='all')
+Symbols['_'] = pg.arrayToQPath(np.array([-0.5, 0.5]), np.array([0, 0]), connect='all')
+Symbols['|'] = pg.arrayToQPath(np.array([0, 0]), np.array([-0.5, 0.5]), connect='all')
+Symbols['x'] = pg.arrayToQPath(
+    np.array([-0.5, 0.5, 0, 0.5, -0.5, 0]), np.array([-0.5, 0.5, 0, -0.5, 0.5, 0]), connect='all'
+)
 
 
 def dealias(**kws):
@@ -171,19 +182,12 @@ def symbol_translator(**kw):
     :return: string
         Code for the relevant pyqtgraph symbol.
     """
-    theta = np.linspace(0, 2 * np.pi, 36)
-    return {  # mpl symbol : pyqt4 symbol
-        '.': pg.arrayToQPath(np.cos(theta) * 0.125, np.sin(theta) * 0.125, connect='all'),
-        ',': pg.arrayToQPath(np.array([-0.01, 0, 0.01, 0, -0.01]),
-                             np.array([0, 0.01, 0, -0.01, 0]), connect='all'),
-        'x': pg.arrayToQPath(np.array([-0.5, 0.5, 0, 0.5, -0.5, 0]),
-                             np.array([-0.5, 0.5, 0, -0.5, 0.5, 0]), connect='all'),
-        '+': '+', '*': 'star', 'o': 'o', 'v': 't', '^': 't1', '>': 't2', '<': 't3',
-        'd': 'd', 's': 's', 'p': 'p', 'h': 'h',
-        '_': pg.arrayToQPath(np.array([-0.5, 0.5]), np.array([0, 0]), connect='all'),
-        '|': pg.arrayToQPath(np.array([0, 0]), np.array([-0.5, 0.5]), connect='all'),
-        'None': None, 'none': None, None: None,
-    }.get(kw['marker'], 'o') if 'marker' in kw else None
+    # mpl symbol : pyqt4 symbol
+    pyqt_symbol = {
+        '.': '.', ',': ',', 'x': 'x', '+': '+', '*': 'star', 'o': 'o', 'v': 't', '^': 't1', '>': 't2', '<': 't3',
+        'd': 'd', 's': 's', 'p': 'p', 'h': 'h', '_': '_', '|': '|', 'None': None, 'none': None, None: None,
+    }.get(kw.get('marker', None), 'o')
+    return pyqt_symbol
 
 
 def symbol_edge_setup(pgkw, plotkw):
diff --git a/test.sh b/test.sh
index 195ad3d..310df8c 100755
--- a/test.sh
+++ b/test.sh
@@ -1,2 +1,2 @@
 #!/bin/bash
-python2.7 -m unittest discover --pattern=*.py -s tests
+python3.7 -m unittest discover --pattern=*.py -s tests
diff --git a/tests/test_translate.py b/tests/test_translate.py
index 762a47d..a81fbaa 100755
--- a/tests/test_translate.py
+++ b/tests/test_translate.py
@@ -86,6 +86,7 @@ def test_style_translator(self):
         assert style_translator(linestyle="-") == QtCore.Qt.SolidLine
 
     def test_symbol_translator(self):
+        from pyqtgraph.graphicsItems.ScatterPlotItem import Symbols
         news = [None] * self.nt
         for i in range(self.nt):
             news[i] = symbol_translator(**self.plot_kw_tests[i])
@@ -95,7 +96,8 @@ def test_symbol_translator(self):
         assert symbol_translator(marker='^') == 't1'
         custom_markers = '_x|,.'
         for custom in custom_markers:
-            assert isinstance(symbol_translator(marker=custom), QtGui.QPainterPath)
+            assert isinstance(symbol_translator(marker=custom), QtGui.QPainterPath) \
+                   or isinstance(Symbols.get(custom, None), QtGui.QPainterPath)
 
     def test_setup_pen_kw(self):
         newp = [None] * self.nt