3 files changed, 12 insertions, 1 deletions

diff --git a/package-lock.json b/package-lock.json
index 2637fdc..2617e32 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -267,6 +267,11 @@
       "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.1.2.tgz",
       "integrity": "sha512-Gd2UZBJDkXlY7GbJxfsE8/nvKkUEU1G38c1siN6QP6a9PT9MmHB8GnpscSmMJSoF8LOIrt8ud/wPtojys4G6+g=="
     },
+    "semver": {
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/semver/-/semver-6.0.0.tgz",
+      "integrity": "sha512-0UewU+9rFapKFnlbirLi3byoOuhrSsli/z/ihNnvM24vgF+8sNBiI1LZPBSH9wJKUwaUbw+s3hToDLCXkrghrQ=="
+    },
     "setimmediate": {
       "version": "1.0.5",
       "resolved": "https://registry.npmjs.org/setimmediate/-/setimmediate-1.0.5.tgz",
diff --git a/package.json b/package.json
index f81e02c..7d55765 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,8 @@
   ],
   "bin": {
     "dhall-to-json": "bin/dhall-to-json.exe",
-    "dhall-to-yaml": "bin/dhall-to-yaml.exe"
+    "dhall-to-yaml": "bin/dhall-to-yaml.exe",
+    "json-to-dhall": "bin/json-to-dhall.exe"
   },
   "scripts": {
     "preinstall": "node ./preinstall.js"
@@ -30,6 +31,7 @@
   "homepage": "https://github.com/cyrilfretlink/node-dhall-json#readme",
   "dependencies": {
     "follow-redirects": "^1.7.0",
+    "semver": "^6.0.0",
     "tar": "^4.4.8",
     "unbzip2-stream": "^1.3.3",
     "unzipper": "^0.9.12"
diff --git a/preinstall.js b/preinstall.js
index 071f159..3fa2382 100644
--- a/preinstall.js
+++ b/preinstall.js
@@ -4,6 +4,7 @@ const fs = require("fs");
 const path = require("path");
 
 const { https } = require("follow-redirects");
+const semver = require("semver");
 const tar = require("tar");
 const unbz2 = require("unbzip2-stream");
 const unzipper = require("unzipper");
@@ -18,6 +19,9 @@ if (!dhallVersion) throw new Error("Missing DHALL_VERSION environment variable."
 
 const dhallJsonVersion = trim(pkg["dhall-json-version"] || process.env.DHALL_JSON_VERSION);
 if (!dhallJsonVersion) throw new Error("Missing DHALL_JSON_VERSION environment variable.");
+if (semver.valid(dhallJsonVersion) && semver.lt(dhallJsonVersion, "1.2.8")) {
+  throw new Error(`This release of the \`${pkg.name}\` npm package installs \`json-to-dhall\`, which isn’t provided by \`dhall-json@<1.2.8\`.`);
+}
 
 const release = `https://github.com/dhall-lang/dhall-haskell/releases/download/${dhallVersion}/dhall-json-${dhallJsonVersion}`;