diff --git a/runtime/Swift/Sources/Antlr4/atn/LexerATNSimulator.swift b/runtime/Swift/Sources/Antlr4/atn/LexerATNSimulator.swift
index 9db7e1de6..5f7f619bf 100644
--- a/runtime/Swift/Sources/Antlr4/atn/LexerATNSimulator.swift
+++ b/runtime/Swift/Sources/Antlr4/atn/LexerATNSimulator.swift
@@ -50,7 +50,7 @@ open class LexerATNSimulator: ATNSimulator {
     }
 
 
-    internal let recog: Lexer?
+    internal weak var recog: Lexer?
 
     /// 
     /// The current token's starting index into the character stream.
diff --git a/runtime/Swift/Sources/Antlr4/atn/ParserATNSimulator.swift b/runtime/Swift/Sources/Antlr4/atn/ParserATNSimulator.swift
index fb0ce0341..ca58b56ef 100644
--- a/runtime/Swift/Sources/Antlr4/atn/ParserATNSimulator.swift
+++ b/runtime/Swift/Sources/Antlr4/atn/ParserATNSimulator.swift
@@ -250,7 +250,8 @@ open class ParserATNSimulator: ATNSimulator {
         }
         return false
     }()
-    internal final var parser: Parser
+
+    internal final unowned let parser: Parser
 
     public final var decisionToDFA: [DFA]