diff --git a/src/cardinality/approx/bipartite.js b/src/cardinality/approx/bipartite.js
index c86c194..8b6445d 100644
--- a/src/cardinality/approx/bipartite.js
+++ b/src/cardinality/approx/bipartite.js
@@ -1,3 +1,3 @@
-import general from './general';
+import general from "./general.js";
 
 export default general;
diff --git a/src/cardinality/approx/general.js b/src/cardinality/approx/general.js
index 83115ca..4402dbf 100644
--- a/src/cardinality/approx/general.js
+++ b/src/cardinality/approx/general.js
@@ -1,4 +1,4 @@
-import general from '../opt/general';
+import general from "../opt/general.js";
 
 const generalApprox = (edges, _eps) => general(edges);
 export default generalApprox;
diff --git a/src/cardinality/approx/index.js b/src/cardinality/approx/index.js
index 70a0b1b..8127fc9 100644
--- a/src/cardinality/approx/index.js
+++ b/src/cardinality/approx/index.js
@@ -1,5 +1,5 @@
-import bipartite from './bipartite';
-import general from './general';
+import bipartite from "./bipartite.js";
+import general from "./general.js";
 
 export default general;
 
diff --git a/src/cardinality/index.js b/src/cardinality/index.js
index 837ad3f..f5f3f15 100644
--- a/src/cardinality/index.js
+++ b/src/cardinality/index.js
@@ -1,5 +1,5 @@
-import approx from './approx';
-import opt from './opt';
+import approx from "./approx/index.js";
+import opt from "./opt/index.js";
 
 export default opt;
 
diff --git a/src/cardinality/opt/bipartite.js b/src/cardinality/opt/bipartite.js
index c86c194..8b6445d 100644
--- a/src/cardinality/opt/bipartite.js
+++ b/src/cardinality/opt/bipartite.js
@@ -1,3 +1,3 @@
-import general from './general';
+import general from "./general.js";
 
 export default general;
diff --git a/src/cardinality/opt/general.js b/src/cardinality/opt/general.js
index 0d39c92..7aece4c 100644
--- a/src/cardinality/opt/general.js
+++ b/src/cardinality/opt/general.js
@@ -1,5 +1,5 @@
-import blossomNoChecks from '../../core/blossomNoChecks';
-import addDefaultWeight from '../../addDefaultWeight';
+import blossomNoChecks from "../../core/blossomNoChecks.js";
+import addDefaultWeight from "../../addDefaultWeight.js";
 
 const general = (edges) => blossomNoChecks(addDefaultWeight(edges), true);
 
diff --git a/src/cardinality/opt/index.js b/src/cardinality/opt/index.js
index 70a0b1b..8127fc9 100644
--- a/src/cardinality/opt/index.js
+++ b/src/cardinality/opt/index.js
@@ -1,5 +1,5 @@
-import bipartite from './bipartite';
-import general from './general';
+import bipartite from "./bipartite.js";
+import general from "./general.js";
 
 export default general;
 
diff --git a/src/core/blossom/blossom.js b/src/core/blossom/blossom.js
index 35643da..750299e 100644
--- a/src/core/blossom/blossom.js
+++ b/src/core/blossom/blossom.js
@@ -1,14 +1,14 @@
 import assert from 'assert';
-import min from './min';
-import rotate from './rotate';
-import verifyOptimum from './verifyOptimum';
-import checkDelta2 from './checkDelta2';
-import checkDelta3 from './checkDelta3';
-import statistics from './statistics';
-import endpoints from './endpoints';
-import neighbours from './neighbours';
-import blossomLeaves from './blossomLeaves';
-import blossomEdges from './blossomEdges';
+import min from "./min.js";
+import rotate from "./rotate.js";
+import verifyOptimum from "./verifyOptimum.js";
+import checkDelta2 from "./checkDelta2.js";
+import checkDelta3 from "./checkDelta3.js";
+import statistics from "./statistics.js";
+import endpoints from "./endpoints.js";
+import neighbours from "./neighbours.js";
+import blossomLeaves from "./blossomLeaves.js";
+import blossomEdges from "./blossomEdges.js";
 
 // Adapted from http://jorisvr.nl/maximummatching.html
 // All credit for the implementation goes to Joris van Rantwijk [http://jorisvr.nl].
diff --git a/src/core/blossom/blossomEdges.js b/src/core/blossom/blossomEdges.js
index 2aeb80c..257249b 100644
--- a/src/core/blossom/blossomEdges.js
+++ b/src/core/blossom/blossomEdges.js
@@ -1,4 +1,4 @@
-import blossomLeaves from './blossomLeaves';
+import blossomLeaves from "./blossomLeaves.js";
 
 export default function* blossomEdges(nvertex, blossomchilds, neighbend, bv) {
 	for (const v of blossomLeaves(nvertex, blossomchilds, bv)) {
diff --git a/src/core/blossom/checkDelta3.js b/src/core/blossom/checkDelta3.js
index 5950e22..7b55d98 100644
--- a/src/core/blossom/checkDelta3.js
+++ b/src/core/blossom/checkDelta3.js
@@ -1,5 +1,5 @@
 import assert from 'assert';
-import blossomLeaves from './blossomLeaves';
+import blossomLeaves from "./blossomLeaves.js";
 
 // Check optimized delta3 against a trivial computation.
 const checkDelta3 = ({
diff --git a/src/core/blossom/index.js b/src/core/blossom/index.js
index 0b14e94..8fa8517 100644
--- a/src/core/blossom/index.js
+++ b/src/core/blossom/index.js
@@ -1,9 +1,9 @@
-import blossom from './blossom';
-import checkDelta2 from './checkDelta2';
-import checkDelta3 from './checkDelta3';
-import min from './min';
-import rotate from './rotate';
-import verifyOptimum from './verifyOptimum';
+import blossom from "./blossom.js";
+import checkDelta2 from "./checkDelta2.js";
+import checkDelta3 from "./checkDelta3.js";
+import min from "./min.js";
+import rotate from "./rotate.js";
+import verifyOptimum from "./verifyOptimum.js";
 
 export default blossom;
 
diff --git a/src/core/blossom/verifyOptimum.js b/src/core/blossom/verifyOptimum.js
index 98fc01a..7b2c0f0 100644
--- a/src/core/blossom/verifyOptimum.js
+++ b/src/core/blossom/verifyOptimum.js
@@ -1,5 +1,5 @@
 import assert from 'assert';
-import min from './min';
+import min from "./min.js";
 
 // Verify that the optimum solution has been reached.
 const verifyOptimum = ({
diff --git a/src/core/blossomNoChecks.js b/src/core/blossomNoChecks.js
index bb47e3e..fc3b2be 100644
--- a/src/core/blossomNoChecks.js
+++ b/src/core/blossomNoChecks.js
@@ -1,4 +1,4 @@
-import blossom from './blossom';
+import blossom from "./blossom/index.js";
 
 const blossomNoChecks = blossom(false, false);
 
diff --git a/src/core/index.js b/src/core/index.js
index 1f4e4ae..42e26b3 100644
--- a/src/core/index.js
+++ b/src/core/index.js
@@ -1,5 +1,5 @@
-import blossom from './blossom';
-import blossomNoChecks from './blossomNoChecks';
+import blossom from "./blossom/index.js";
+import blossomNoChecks from "./blossomNoChecks.js";
 
 /* eslint import/no-anonymous-default-export: [2, {"allowObject": true}] */
 export default {
diff --git a/src/index.js b/src/index.js
index 4a3e251..db5ab12 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,8 +1,8 @@
-import cardinality from './cardinality';
-import core from './core';
-import weight from './weight';
-import iter from './iter';
-import addDefaultWeight from './addDefaultWeight';
+import cardinality from "./cardinality/index.js";
+import core from "./core/index.js";
+import weight from "./weight/index.js";
+import iter from "./iter.js";
+import addDefaultWeight from "./addDefaultWeight.js";
 
 export default weight;
 
diff --git a/src/weight/approx/bipartite.js b/src/weight/approx/bipartite.js
index c86c194..8b6445d 100644
--- a/src/weight/approx/bipartite.js
+++ b/src/weight/approx/bipartite.js
@@ -1,3 +1,3 @@
-import general from './general';
+import general from "./general.js";
 
 export default general;
diff --git a/src/weight/approx/general.js b/src/weight/approx/general.js
index 83115ca..4402dbf 100644
--- a/src/weight/approx/general.js
+++ b/src/weight/approx/general.js
@@ -1,4 +1,4 @@
-import general from '../opt/general';
+import general from "../opt/general.js";
 
 const generalApprox = (edges, _eps) => general(edges);
 export default generalApprox;
diff --git a/src/weight/approx/index.js b/src/weight/approx/index.js
index 70a0b1b..8127fc9 100644
--- a/src/weight/approx/index.js
+++ b/src/weight/approx/index.js
@@ -1,5 +1,5 @@
-import bipartite from './bipartite';
-import general from './general';
+import bipartite from "./bipartite.js";
+import general from "./general.js";
 
 export default general;
 
diff --git a/src/weight/index.js b/src/weight/index.js
index 837ad3f..f5f3f15 100644
--- a/src/weight/index.js
+++ b/src/weight/index.js
@@ -1,5 +1,5 @@
-import approx from './approx';
-import opt from './opt';
+import approx from "./approx/index.js";
+import opt from "./opt/index.js";
 
 export default opt;
 
diff --git a/src/weight/opt/bipartite.js b/src/weight/opt/bipartite.js
index c86c194..8b6445d 100644
--- a/src/weight/opt/bipartite.js
+++ b/src/weight/opt/bipartite.js
@@ -1,3 +1,3 @@
-import general from './general';
+import general from "./general.js";
 
 export default general;
diff --git a/src/weight/opt/general.js b/src/weight/opt/general.js
index b97a3f3..cb86103 100644
--- a/src/weight/opt/general.js
+++ b/src/weight/opt/general.js
@@ -1,4 +1,4 @@
-import blossomNoChecks from '../../core/blossomNoChecks';
+import blossomNoChecks from "../../core/blossomNoChecks.js";
 
 const general = (edges) => blossomNoChecks(edges);
 
diff --git a/src/weight/opt/index.js b/src/weight/opt/index.js
index 70a0b1b..8127fc9 100644
--- a/src/weight/opt/index.js
+++ b/src/weight/opt/index.js
@@ -1,5 +1,5 @@
-import bipartite from './bipartite';
-import general from './general';
+import bipartite from "./bipartite.js";
+import general from "./general.js";
 
 export default general;
 
diff --git a/test/src/cardinality.js b/test/src/cardinality.js
index 89fcd15..9739f96 100644
--- a/test/src/cardinality.js
+++ b/test/src/cardinality.js
@@ -1,9 +1,9 @@
 import test from 'ava';
 import {enumerate} from '@aureooms/js-itertools';
 
-import maximumCardinalityMatching from '../../src/cardinality';
-import {addDefaultWeight} from '../../src';
-import blossom from '../../src/core/blossom';
+import maximumCardinalityMatching from "../../src/cardinality/index.js";
+import {addDefaultWeight} from "../../src/index.js";
+import blossom from "../../src/core/blossom/index.js";
 
 const macro = (t, algorithm, edges, expected) => {
 	const input = edges.map((edge) => edge.slice()); // Deepcopy
diff --git a/test/src/readme.js b/test/src/readme.js
index b25c077..67e62d1 100644
--- a/test/src/readme.js
+++ b/test/src/readme.js
@@ -1,7 +1,7 @@
 import test from 'ava';
 
-import maximumMatching, {iter} from '../../src';
-import maximumCardinalityMatching from '../../src/cardinality';
+import maximumMatching, {iter} from "../../src/index.js";
+import maximumCardinalityMatching from "../../src/cardinality/index.js";
 
 test('weight', (t) => {
 	const edges = [
diff --git a/test/src/weight.js b/test/src/weight.js
index 49bd4ae..3ff023f 100644
--- a/test/src/weight.js
+++ b/test/src/weight.js
@@ -1,8 +1,8 @@
 import test from 'ava';
 import {enumerate} from '@aureooms/js-itertools';
 
-import maximumMatching from '../../src';
-import blossom from '../../src/core/blossom';
+import maximumMatching from "../../src/index.js";
+import blossom from "../../src/core/blossom/index.js";
 
 const macro = (t, algorithm, edges, expected) => {
 	const input = edges.map((edge) => edge.slice()); // Deepcopy