diff --git a/bin/process-git-diff.js b/bin/process-git-diff.js
new file mode 100644
index 0000000000000..b80b117daa59e
--- /dev/null
+++ b/bin/process-git-diff.js
@@ -0,0 +1,34 @@
+// npm will introduce changes to a `package-lock.json` file for optional
+// dependencies varying on environment. If the only changes are the
+// addition of an "optional" flag in `package-lock.json` file from
+// `git diff`: we ignore the results.
+//
+// See: https://github.com/npm/npm/issues/17722
+
+// Example usage:
+//
+// git diff -U0 | xargs -0 node bin/process-git-diff
+
+// Example input:
+//
+// diff --git a/package-lock.json b/package-lock.json
+// index e8c8a25dc..251af8689 100644
+// --- a/package-lock.json
+// +++ b/package-lock.json
+// @@ -14373 +14373,2 @@
+// -                       "dev": true
+// +                       "dev": true,
+// +                       "optional": true
+// @@ -14648 +14649,2 @@
+// -                       "dev": true
+// +                       "dev": true,
+// +                       "optional": true
+
+const hasNonOptionalDiff = !! ( process.argv[ 2 ] || '' )
+	// Strip individual diffs of optional-only.
+	.replace( /@@ .+ @@\n(-.+\n\+.+,\n)?\+.+\"optional\": true,?\n/gm, '' )
+	// If no more line diffs remain after above, remove diff heading for file.
+	.replace( /diff --git a\/package-lock.json b\/package-lock.json\nindex \w+..\w+ \d+\n--- a\/package-lock.json\n\+\+\+ b\/package-lock.json\n(?!@@)/, '' );
+
+// Exit with error code if, after replace, changes still exist.
+process.exit( hasNonOptionalDiff ? 1 : 0 );
diff --git a/package.json b/package.json
index 7a31c83725846..1b8e0ce2e6c2c 100644
--- a/package.json
+++ b/package.json
@@ -151,7 +151,9 @@
 		"build": "npm run build:packages && cross-env NODE_ENV=production webpack",
 		"check-engines": "check-node-version --package",
 		"check-licenses": "concurrently \"wp-scripts check-licenses --prod --gpl2\" \"wp-scripts check-licenses --dev\"",
-		"ci": "concurrently \"npm run lint\" \"npm run test-unit:coverage-ci\"",
+		"precheck-local-changes": "npm run docs:build",
+		"check-local-changes": "( git diff -U0 | xargs -0 node bin/process-git-diff ) || ( echo \"There are local uncommitted changes after one or both of 'npm install' or 'npm run docs:build'!\" && exit 1 );",
+		"ci": "concurrently \"npm run lint\" \"npm run test-unit:coverage-ci\" \"npm run check-local-changes\"",
 		"predev": "npm run check-engines",
 		"dev": "npm run build:packages && concurrently \"cross-env webpack --watch\" \"npm run dev:packages\"",
 		"dev:packages": "node ./bin/packages/watch.js",