webpack
diff --git a/‎lib/Compilation.js‎
Lines changed: 3 additions & 2 deletions b/‎lib/Compilation.js‎
Lines changed: 3 additions & 2 deletions
diff --git a/‎lib/LazyBarrel.js‎
Lines changed: 8 additions & 0 deletions b/‎lib/LazyBarrel.js‎
Lines changed: 8 additions & 0 deletions
@@ -1869,8 +1869,9 @@ BREAKING CHANGE: Asset processing hooks in Compilation has been merged into a si
 			this.moduleGraph.setParents(dep, currentBlock, module, index);
 			if (
 				hasLazyBarrel &&
-				// `isLazy` may be missing on custom dependency types not extending the base Dependency
-				typeof dep.isLazy === "function" &&
+				// TODO remove in webpack 6
+				// It may be missing on custom dependency types not extending the base Dependency
+				"isLazy" in dep &&
 				dep.isLazy()
 			) {
 				return;
 
@@ -45,6 +45,10 @@ function getForwardedIds(dependencies) {
 	/** @type {Set<string>} */
 	const ids = new Set();
 	for (const dependency of dependencies) {
+		// TODO remove in webpack 6
+		// It may be missing on custom dependency types not extending the base Dependency
+		if (!("getForwardId" in dependency)) continue;
+
 		const id = dependency.getForwardId();
 		if (id === true) return true;
 		if (id !== null) ids.add(id);
@@ -201,6 +205,10 @@ class LazyBarrelController {
 		/** @type {LazyBarrelInfo | undefined} */
 		let info;
 		for (const dep of module.dependencies) {
+			// TODO remove in webpack 6
+			// It may be missing on custom dependency types not extending the base Dependency
+			if (!("getLazyUntil" in dep && "setLazy" in dep)) continue;
+
 			const until = dep.getLazyUntil();
 			if (until === null) continue;
 			if (info === undefined) info = new LazyBarrelInfo();