diff --git a/src/path/string.js b/src/path/string.js
index f2a084f..02e57b0 100644
--- a/src/path/string.js
+++ b/src/path/string.js
@@ -3,9 +3,11 @@ export default function PathString() {
 }
 
 PathString.prototype = {
+  _radius: 4.5,
   _circle: circle(4.5),
   pointRadius: function(_) {
-    return this._circle = circle(_), this;
+    if ((_ = +_) !== this._radius) this._radius = _, this._circle = null;
+    return this;
   },
   polygonStart: function() {
     this._line = 0;
@@ -32,6 +34,7 @@ PathString.prototype = {
         break;
       }
       default: {
+        if (this._circle == null) this._circle = circle(this._radius);
         this._string.push("M", x, ",", y, this._circle);
         break;
       }
diff --git a/test/path/string-test.js b/test/path/string-test.js
index fab5189..26caa60 100644
--- a/test/path/string-test.js
+++ b/test/path/string-test.js
@@ -21,6 +21,16 @@ tape("geoPath(Point) renders a point", function(test) {
   test.end();
 });
 
+tape("geoPath.pointRadius(radius)(Point) renders a point of the given radius", function(test) {
+  test.pathEqual(d3_geo.geoPath()
+      .projection(equirectangular)
+      .pointRadius(10)({
+    type: "Point",
+    coordinates: [-63, 18]
+  }), "M165,160m0,10a10,10 0 1,1 0,-20a10,10 0 1,1 0,20z");
+  test.end();
+});
+
 tape("geoPath(MultiPoint) renders a point", function(test) {
   test.pathEqual(testPath(equirectangular, {
     type: "MultiPoint",