diff --git a/src/collide.js b/src/collide.js
index e5f2863..c87878e 100644
--- a/src/collide.js
+++ b/src/collide.js
@@ -1,6 +1,6 @@
-import constant from "./constant";
-import jiggle from "./jiggle";
 import {quadtree} from "d3-quadtree";
+import constant from "./constant.js";
+import jiggle from "./jiggle.js";
 
 function x(d) {
   return d.x + d.vx;
diff --git a/src/link.js b/src/link.js
index 8b3f722..6a5d616 100644
--- a/src/link.js
+++ b/src/link.js
@@ -1,5 +1,5 @@
-import constant from "./constant";
-import jiggle from "./jiggle";
+import constant from "./constant.js";
+import jiggle from "./jiggle.js";
 
 function index(d) {
   return d.index;
diff --git a/src/manyBody.js b/src/manyBody.js
index eb45e9c..045a401 100644
--- a/src/manyBody.js
+++ b/src/manyBody.js
@@ -1,7 +1,7 @@
-import constant from "./constant";
-import jiggle from "./jiggle";
 import {quadtree} from "d3-quadtree";
-import {x, y} from "./simulation";
+import constant from "./constant.js";
+import jiggle from "./jiggle.js";
+import {x, y} from "./simulation.js";
 
 export default function() {
   var nodes,
diff --git a/src/radial.js b/src/radial.js
index 517144d..609516b 100644
--- a/src/radial.js
+++ b/src/radial.js
@@ -1,4 +1,4 @@
-import constant from "./constant";
+import constant from "./constant.js";
 
 export default function(radius, x, y) {
   var nodes,
diff --git a/src/x.js b/src/x.js
index 894e748..2e7a821 100644
--- a/src/x.js
+++ b/src/x.js
@@ -1,4 +1,4 @@
-import constant from "./constant";
+import constant from "./constant.js";
 
 export default function(x) {
   var strength = constant(0.1),
diff --git a/src/y.js b/src/y.js
index bdf68e4..5fcde67 100644
--- a/src/y.js
+++ b/src/y.js
@@ -1,4 +1,4 @@
-import constant from "./constant";
+import constant from "./constant.js";
 
 export default function(y) {
   var strength = constant(0.1),