diff --git a/gns3server/utils/picture.py b/gns3server/utils/picture.py
index dad421e0..50d17996 100644
--- a/gns3server/utils/picture.py
+++ b/gns3server/utils/picture.py
@@ -99,8 +99,8 @@ def get_size(data, default_width=0, default_height=0):
         root = tree.getroot()
 
         try:
-            width = _svg_convert_size(root.attrib.get("width", 0))
-            height = _svg_convert_size(root.attrib.get("height", 0))
+            width = _svg_convert_size(root.attrib.get("width", "0"))
+            height = _svg_convert_size(root.attrib.get("height", "0"))
         except IndexError:
             raise ValueError("Invalid SVG file")