diff --git a/svgpathtools/svg_to_paths.py b/svgpathtools/svg_to_paths.py
index cf964e0..4023cd2 100644
--- a/svgpathtools/svg_to_paths.py
+++ b/svgpathtools/svg_to_paths.py
@@ -24,6 +24,7 @@ def path2pathd(path):
     return path['d']
 
 
+
 def ellipse2pathd(ellipse):
     """converts the parameters from an ellipse or a circle to a string for a 
     Path object d-attribute"""
@@ -91,17 +92,26 @@ def rect2pathd(rect):
     x, y = float(rect.get('x', 0)), float(rect.get('y', 0))
     w, h = float(rect.get('width', 0)), float(rect.get('height', 0))
     if 'rx' in rect or 'ry' in rect:
-        rx = float(rect.get('rx', 0))
-        ry = float(rect.get('ry', 0))
-        d = "M {} {} ".format(x + rx, y) # right of p0
-        d += "L {} {} ".format(x + w - rx, y) # go to p1
-        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x+w, y+ry) # arc for p1
-        d += "L {} {} ".format(x+w, y+h-ry) # above p2
-        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x+w-rx, y+h) # arc for p2
-        d += "L {} {} ".format(x+rx, y+h) # right of p3
-        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x, y+h-ry) # arc for p3
-        d += "L {} {} ".format(x, y+ry) # below p0
-        d += "A {} {} 0 0 1 {} {} z".format(rx, ry, x+rx, y) # arc for p0
+
+        # if only one, rx or ry, is present, use that value for both
+        # https://developer.mozilla.org/en-US/docs/Web/SVG/Element/rect
+        rx = rect.get('rx', None)
+        ry = rect.get('ry', None)
+        if rx is None:
+            rx = ry or 0.
+        if ry is None:
+            ry = rx or 0.
+        rx, ry = float(rx), float(ry)
+
+        d = "M {} {} ".format(x + rx, y)  # right of p0
+        d += "L {} {} ".format(x + w - rx, y)  # go to p1
+        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x+w, y+ry)  # arc for p1
+        d += "L {} {} ".format(x+w, y+h-ry)  # above p2
+        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x+w-rx, y+h)  # arc for p2
+        d += "L {} {} ".format(x+rx, y+h)  # right of p3
+        d += "A {} {} 0 0 1 {} {} ".format(rx, ry, x, y+h-ry)  # arc for p3
+        d += "L {} {} ".format(x, y+ry)  # below p0
+        d += "A {} {} 0 0 1 {} {} z".format(rx, ry, x+rx, y)  # arc for p0
         return d
 
     x0, y0 = x, y