diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
index ab8c255680c7..68e534aa8c58 100644
--- a/lib/matplotlib/backends/backend_qt5.py
+++ b/lib/matplotlib/backends/backend_qt5.py
@@ -182,8 +182,13 @@ class FigureCanvasQT(QtWidgets.QWidget, FigureCanvasBase):
                # QtCore.Qt.XButton2: None,
                }
 
+    def _update_figure_dpi(self):
+        dpi = self._dpi_ratio * self.figure._original_dpi
+        self.figure._set_dpi(dpi, forward=False)
+
     def __init__(self, figure):
         _create_qApp()
+        figure._original_dpi = figure.dpi
 
         # NB: Using super for this call to avoid a TypeError:
         # __init__() takes exactly 2 arguments (1 given) on QWidget
@@ -192,6 +197,8 @@ def __init__(self, figure):
         # http://pyqt.sourceforge.net/Docs/PyQt5/pyqt4_differences.html#cooperative-multi-inheritance
         super(FigureCanvasQT, self).__init__(figure=figure)
         self.figure = figure
+        self._update_figure_dpi()
+
         self.setMouseTracking(True)
         w, h = self.get_width_height()
         self.resize(w, h)
diff --git a/lib/matplotlib/backends/backend_qt5agg.py b/lib/matplotlib/backends/backend_qt5agg.py
index b7a90a8f4d68..78d9fdada4f6 100644
--- a/lib/matplotlib/backends/backend_qt5agg.py
+++ b/lib/matplotlib/backends/backend_qt5agg.py
@@ -190,17 +190,6 @@ class FigureCanvasQTAgg(FigureCanvasQTAggBase, FigureCanvasQT):
 
     """
 
-    def __init__(self, figure):
-        super(FigureCanvasQTAgg, self).__init__(figure=figure)
-        # We don't want to scale up the figure DPI more than once.
-        # Note, we don't handle a signal for changing DPI yet.
-        self.figure._original_dpi = self.figure.dpi
-        self._update_figure_dpi()
-
-    def _update_figure_dpi(self):
-        dpi = self._dpi_ratio * self.figure._original_dpi
-        self.figure._set_dpi(dpi, forward=False)
-
 
 @_BackendQT5.export
 class _BackendQT5Agg(_BackendQT5):
diff --git a/lib/matplotlib/tests/test_backend_qt5.py b/lib/matplotlib/tests/test_backend_qt5.py
index dc47afecc719..3f4bab6fa4f1 100644
--- a/lib/matplotlib/tests/test_backend_qt5.py
+++ b/lib/matplotlib/tests/test_backend_qt5.py
@@ -125,6 +125,7 @@ def test_dpi_ratio_change():
         size = qt_canvas.size()
 
         qt_canvas.manager.show()
+        qt_canvas.draw()
         qApp.processEvents()
 
         # The DPI and the renderer width/height change
@@ -133,8 +134,8 @@ def test_dpi_ratio_change():
         assert qt_canvas.renderer.height == 720
 
         # The actual widget size and figure physical size don't change
-        assert size.width() == 200
-        assert size.height() == 80
+        assert size.width() == 600
+        assert size.height() == 240
         assert_equal(qt_canvas.get_width_height(), (600, 240))
         assert_equal(fig.get_size_inches(), (5, 2))
 
@@ -151,7 +152,7 @@ def test_dpi_ratio_change():
         assert qt_canvas.renderer.height == 480
 
         # The actual widget size and figure physical size don't change
-        assert size.width() == 200
-        assert size.height() == 80
+        assert size.width() == 600
+        assert size.height() == 240
         assert_equal(qt_canvas.get_width_height(), (600, 240))
         assert_equal(fig.get_size_inches(), (5, 2))