diff --git a/src/hooks/useCellar.test.ts b/src/hooks/useCellar.test.ts
index 86f21cd..753c881 100644
--- a/src/hooks/useCellar.test.ts
+++ b/src/hooks/useCellar.test.ts
@@ -1,4 +1,4 @@
-import { assertEquals } from "deno/testing/asserts.ts"
+import { assertEquals, assertRejects } from "deno/testing/asserts.ts"
 import SemVer, * as semver from "../utils/semver.ts"
 import { useTestConfig } from "./useTestConfig.ts"
 import install from "../plumbing/install.ts"
@@ -14,6 +14,8 @@ Deno.test("useCellar.resolve()", async () => {
   await useCellar().resolve(installation.pkg)
   await useCellar().resolve({ project: "python.org", constraint: new semver.Range("^3") })
   await useCellar().resolve(installation.path)
+
+  assertRejects(() => useCellar().resolve({ project: "python.org", constraint: new semver.Range("@300")}))
 })
 
 Deno.test("useCellar.has()", async () => {
diff --git a/src/plumbing/resolve.test.ts b/src/plumbing/resolve.test.ts
index a1701b1..126f46b 100644
--- a/src/plumbing/resolve.test.ts
+++ b/src/plumbing/resolve.test.ts
@@ -1,8 +1,10 @@
+import { assert, assertEquals, fail, assertRejects } from "deno/testing/asserts.ts"
 import { Installation, Package, PackageRequirement } from "../types.ts"
-import { assert, assertEquals, fail } from "deno/testing/asserts.ts"
 import { useTestConfig } from "../hooks/useTestConfig.ts"
+import useInventory from "../hooks/useInventory.ts"
 import resolve, { _internals } from "./resolve.ts"
 import useCellar from "../hooks/useCellar.ts"
+import * as semver from "../utils/semver.ts"
 import { stub } from "deno/testing/mock.ts"
 import SemVer from "../utils/semver.ts"
 import Path from "../utils/Path.ts"
@@ -58,7 +60,7 @@ Deno.test("resolve cellar.has", async runner => {
     assert(errord)
   })
 
-  await runner.step("uses existing version if  even if update set", async () => {
+  await runner.step("uses existing version if even if update set", async () => {
     const stub1 = stub(_internals, "useInventory", () => ({
       get: () => fail(),
       select: () => Promise.resolve(pkg.version),
@@ -77,3 +79,73 @@ Deno.test("resolve cellar.has", async runner => {
     }
   })
 })
+
+const permissions = { net: false, read: true, env: ["TMPDIR", "HOME", "TMP", "TEMP"], write: true /*FIXME*/ }
+
+// https://github.com/teaxyz/cli/issues/655
+Deno.test("postgres@500 fails", { permissions }, async () => {
+  useTestConfig()
+
+  const pkg = {
+    project: "posqtgres.org",
+    version: new SemVer("15.0.1")
+  }
+
+  const select = useInventory().select
+  const stub1 = stub(_internals, "useInventory", () => ({
+    get: () => Promise.resolve([pkg.version]),
+    select,
+  }))
+
+  const pkgs = [
+    { project: pkg.project, constraint: new semver.Range('@500') }
+  ]
+
+  try {
+    // https://github.com/teaxyz/cli/issues/655
+    await assertRejects(() => resolve(pkgs))
+  } finally {
+    stub1.restore()
+  }
+})
+
+// https://github.com/teaxyz/cli/issues/655
+Deno.test("postgres@500 fails if installed", { permissions }, async () => {
+  const pkg = {
+    project: "posqtgres.org",
+    version: new SemVer("15.0.1")
+  }
+  const prefix = useTestConfig().prefix
+
+  const cellar = useCellar()
+  const has = (b: Path | Package | PackageRequirement) => {
+    if ("constraint" in b && b.constraint.satisfies(pkg.version)) {
+      const a: Installation = {pkg, path: prefix.join(pkg.project, `v${pkg.version}`) }
+      return Promise.resolve(a)
+    } else {
+      return Promise.resolve(undefined)
+    }
+  }
+
+  const select = useInventory().select
+  const stub1 = stub(_internals, "useInventory", () => ({
+    get: () => Promise.resolve([pkg.version]),
+    select,
+  }))
+  const stub2 = stub(_internals, "useCellar", () => ({
+    ...cellar,
+    has
+  }))
+
+  const pkgs = [
+    { project: pkg.project, constraint: new semver.Range('@500') }
+  ]
+
+  try {
+    // https://github.com/teaxyz/cli/issues/655
+    await assertRejects(() => resolve(pkgs))
+  } finally {
+    stub1.restore()
+    stub2.restore()
+  }
+})
diff --git a/src/utils/semver.test.ts b/src/utils/semver.test.ts
index 523d3e6..17f7384 100644
--- a/src/utils/semver.test.ts
+++ b/src/utils/semver.test.ts
@@ -45,6 +45,10 @@ Deno.test("semver", async test => {
 
   await test.step("satisfies", () => {
     assertEquals(new semver.Range("=3.1.0").max([new SemVer("3.1.0")]), new SemVer("3.1.0"))
+
+    // the following two test for https://github.com/teaxyz/lib/pull/36
+    assertEquals(new semver.Range("^300").max([new SemVer("3.1.0")]), undefined)
+    assertEquals(new semver.Range("@300").max([new SemVer("3.1.0")]), undefined)
   })
 
   await test.step("constructor", () => {
@@ -153,6 +157,10 @@ Deno.test("semver", async test => {
     assertThrows(() => new semver.Range("1.2"))
     assertThrows(() => new semver.Range("1.2.3"))
     assertThrows(() => new semver.Range("1.2.3.4"))
+
+    assertEquals(new semver.Range("@300").toString(), "^300")
+    assertEquals(new semver.Range("@300.1").toString(), "~300.1")
+    assertEquals(new semver.Range("@300.1.0").toString(), ">=300.1<300.1.1")
   })
 
   await test.step("intersection", async test => {
diff --git a/src/utils/semver.ts b/src/utils/semver.ts
index 2ceaed8..69e81a0 100644
--- a/src/utils/semver.ts
+++ b/src/utils/semver.ts
@@ -53,7 +53,7 @@ export default class SemVer {
       this.raw = v.raw
       this.pretty = v.pretty
     } else {
-      this.components = input
+      this.components = [...input]
       this.raw = input.join('.')
     }