diff --git a/lib/svgpath.js b/lib/svgpath.js
index bc6d50e..857d136 100644
--- a/lib/svgpath.js
+++ b/lib/svgpath.js
@@ -496,6 +496,11 @@ SvgPath.prototype.unarc = function () {
       nextY = s[7];
     }
 
+    // one of the radii is zero, treating it as a line segment instead
+    if (s[1] === 0 || s[2] === 0) {
+      return [ [ 'L', nextX, nextY ] ];
+    }
+
     new_segments = a2c(x, y, nextX, nextY, s[4], s[5], s[1], s[2], s[3]);
 
     new_segments.forEach(function (s) {
diff --git a/test/api.js b/test/api.js
index 0db26bc..c3aa0b8 100644
--- a/test/api.js
+++ b/test/api.js
@@ -491,13 +491,13 @@ describe('API', function () {
       // both rx and ry are zero
       assert.equal(
         svgpath('M100 100A0 0 0 0 1 110 110').unarc().round(0).toString(),
-        'M100 100'
+        'M100 100L110 110'
       );
 
       // rx is zero
       assert.equal(
         svgpath('M100 100A0 100 0 0 1 110 110').unarc().round(0).toString(),
-        'M100 100'
+        'M100 100L110 110'
       );
     });
   });