diff --git a/silx/gui/plot/backends/BackendOpenGL.py b/silx/gui/plot/backends/BackendOpenGL.py
index e772882255..a9a0f9375e 100755
--- a/silx/gui/plot/backends/BackendOpenGL.py
+++ b/silx/gui/plot/backends/BackendOpenGL.py
@@ -230,6 +230,9 @@ def __init__(self, plot, parent=None, f=qt.Qt.WindowFlags()):
             foregroundColor=(0., 0., 0., 1.),
             gridColor=(.7, .7, .7, 1.),
             marginRatios=(.15, .1, .1, .15))
+        self._plotFrame.size = (  # Init size with size int
+            int(self.getDevicePixelRatio() * 640),
+            int(self.getDevicePixelRatio() * 480))
 
         # Make postRedisplay asynchronous using Qt signal
         self._sigPostRedisplay.connect(