diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 703321c3ca..139ee5fa43 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1658,6 +1658,16 @@ void GLCanvas3D::render_thumbnail(ThumbnailData& thumbnail_data, unsigned int w,
     static const float orange[] = { 0.99f, 0.49f, 0.26f };
     static const float gray[] = { 0.64f, 0.64f, 0.64f };
 
+    const Size& cnv_size = get_canvas_size();
+    unsigned int cnv_w = (unsigned int)cnv_size.get_width();
+    unsigned int cnv_h = (unsigned int)cnv_size.get_height();
+    if ((w > cnv_w) || (h > cnv_h))
+    {
+        float ratio = std::min((float)cnv_w / (float)w, (float)cnv_h / (float)h);
+        w = (unsigned int)(ratio * (float)w);
+        h = (unsigned int)(ratio * (float)h);
+    }
+
     thumbnail_data.set(w, h);
 
     GLVolumePtrs visible_volumes;
@@ -1720,7 +1730,6 @@ void GLCanvas3D::render_thumbnail(ThumbnailData& thumbnail_data, unsigned int w,
 #endif 
 
     // restore the framebuffer size to avoid flickering on the 3D scene
-    const Size& cnv_size = get_canvas_size();
     m_camera.apply_viewport(0, 0, cnv_size.get_width(), cnv_size.get_height());
 }
 #endif // ENABLE_THUMBNAIL_GENERATOR