diff --git a/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java b/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
index 9b246d3b7..79c6c73e5 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
@@ -103,7 +103,9 @@ public class LexerATNSimulator extends ATNSimulator {
 	}
 
 	public int match(CharStream input, int mode) {
-		match_calls++;
+		synchronized (LexerATNSimulator.class) {
+			match_calls++;
+		}
 		this.mode = mode;
 		int mark = input.mark();
 		try {