diff --git a/src/generic/subtract.concrete.mjs b/src/generic/subtract.concrete.mjs
new file mode 100644
index 0000000..39638aa
--- /dev/null
+++ b/src/generic/subtract.concrete.mjs
@@ -0,0 +1,3 @@
+export {subtract} from './subtract.mjs'
+export * from '../number/add.mjs'
+export * from '../number/negate.mjs'
diff --git a/test/custom.mjs b/test/custom.mjs
index aabbb8c..72ba2d0 100644
--- a/test/custom.mjs
+++ b/test/custom.mjs
@@ -6,6 +6,7 @@ import * as numberAdd from '../src/number/add.mjs'
 import * as complex from '../src/complex/all.mjs'
 import * as complexAdd from '../src/complex/add.mjs'
 import * as complexNegate from '../src/complex/negate.mjs'
+import * as concreteSubtract from '../src/generic/subtract.concrete.mjs'
 import extendToComplex from '../src/complex/extendToComplex.mjs'
 
 const bw = new PocomathInstance('backwards')
@@ -55,4 +56,10 @@ describe('A custom instance', () => {
       assert.strictEqual('subtract' in cherry, false)
       assert.strictEqual('negate' in cherry, false)
    })
+
+   it("can use bundles that are closed under dependency", () => {
+      const ok = new PocomathInstance('concrete')
+      ok.install(concreteSubtract)
+      assert.strictEqual(ok.subtract(7, 5), 2)
+   })
 })