diff --git a/.travis.yml b/.travis.yml
index 4f912c0fa2d0..1f1d19aa03a0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -43,6 +43,7 @@ env:
     - NPROC=2
     - TEST_ARGS=--no-pep8
     - NOSE_ARGS="--processes=$NPROC --process-timeout=300"
+    - PYTHON_ARGS=
 
 language: python
 
@@ -51,6 +52,7 @@ matrix:
     - python: 2.7
       env: MOCK=mock NUMPY=numpy==1.6
     - python: 3.4
+      env: PYTHON_ARGS=-OO
     - python: 3.5
       env: PANDAS=pandas NOSE_ARGS=--with-coverage
     - python: 3.5
@@ -140,7 +142,7 @@ script:
       if [[ $TRAVIS_OS_NAME == 'osx' ]]; then
         python tests.py $NOSE_ARGS $TEST_ARGS
       else 
-        gdb -return-child-result -batch -ex r -ex bt --args python tests.py $NOSE_ARGS $TEST_ARGS
+        gdb -return-child-result -batch -ex r -ex bt --args python $PYTHON_ARGS tests.py $NOSE_ARGS $TEST_ARGS
       fi
     else
       cd doc
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
index 2b99261b9c85..6bff60503296 100755
--- a/lib/mpl_toolkits/mplot3d/axes3d.py
+++ b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -746,19 +746,21 @@ def get_xlim3d(self):
         return self.xy_viewLim.intervalx
     get_xlim3d.__doc__ = maxes.Axes.get_xlim.__doc__
     get_xlim = get_xlim3d
-    get_xlim.__doc__ += """
-        .. versionchanged :: 1.1.0
-            This function now correctly refers to the 3D x-limits
-        """
+    if get_xlim.__doc__ is not None:
+        get_xlim.__doc__ += """
+            .. versionchanged :: 1.1.0
+                This function now correctly refers to the 3D x-limits
+            """
 
     def get_ylim3d(self):
         return self.xy_viewLim.intervaly
     get_ylim3d.__doc__ = maxes.Axes.get_ylim.__doc__
     get_ylim = get_ylim3d
-    get_ylim.__doc__ += """
-        .. versionchanged :: 1.1.0
-            This function now correctly refers to the 3D y-limits.
-        """
+    if get_ylim.__doc__ is not None:
+        get_ylim.__doc__ += """
+            .. versionchanged :: 1.1.0
+                This function now correctly refers to the 3D y-limits.
+            """
 
     def get_zlim3d(self):
         '''Get 3D z limits.'''
@@ -780,22 +782,24 @@ def set_xscale(self, value, **kwargs) :
         self.xaxis._set_scale(value, **kwargs)
         self.autoscale_view(scaley=False, scalez=False)
         self._update_transScale()
-    set_xscale.__doc__ = maxes.Axes.set_xscale.__doc__ + """
+    if maxes.Axes.set_xscale.__doc__ is not None:
+        set_xscale.__doc__ = maxes.Axes.set_xscale.__doc__ + """
 
-        .. versionadded :: 1.1.0
-            This function was added, but not tested. Please report any bugs.
-        """
+            .. versionadded :: 1.1.0
+                This function was added, but not tested. Please report any bugs.
+            """
 
     def set_yscale(self, value, **kwargs) :
         self.yaxis._set_scale(value, **kwargs)
         self.autoscale_view(scalex=False, scalez=False)
         self._update_transScale()
         self.stale = True
-    set_yscale.__doc__ = maxes.Axes.set_yscale.__doc__ + """
+    if maxes.Axes.set_yscale.__doc__ is not None:
+        set_yscale.__doc__ = maxes.Axes.set_yscale.__doc__ + """
 
-        .. versionadded :: 1.1.0
-            This function was added, but not tested. Please report any bugs.
-        """
+            .. versionadded :: 1.1.0
+                This function was added, but not tested. Please report any bugs.
+            """
 
     @docstring.dedent_interpd
     def set_zscale(self, value, **kwargs) :
diff --git a/tests.py b/tests.py
index 35d112b034a8..db19f5572772 100755
--- a/tests.py
+++ b/tests.py
@@ -53,4 +53,6 @@ def run(extra_args):
         extra_args.extend(['-a', '!network'])
         sys.argv.remove('--no-network')
 
+    print('Python byte-compilation optimization level: %d' % sys.flags.optimize)
+
     run(extra_args)