diff --git a/lib/Parser.js b/lib/Parser.js
index 721bf3db192..7ef197866c6 100644
--- a/lib/Parser.js
+++ b/lib/Parser.js
@@ -2061,6 +2061,12 @@ class Parser extends Tapable {
 
 		this.scope = oldScope;
 	}
+	
+	// TODO webpack 5: remove this methods
+	// only for backward-compat
+	detectStrictMode(statements) {
+		this.detectMode(statements);
+	}
 
 	detectMode(statements) {
 		const isLiteral =