diff --git a/tool/resources/org/antlr/v4/tool/templates/codegen/JavaScript/JavaScript.stg b/tool/resources/org/antlr/v4/tool/templates/codegen/JavaScript/JavaScript.stg
index f2476a2588..01947f0745 100644
--- a/tool/resources/org/antlr/v4/tool/templates/codegen/JavaScript/JavaScript.stg
+++ b/tool/resources/org/antlr/v4/tool/templates/codegen/JavaScript/JavaScript.stg
@@ -466,9 +466,9 @@ TestSetInline(s) ::= <<
 <s.bitsets:{bits | <if(rest(rest(bits.ttypes)))><bitsetBitfieldComparison(s, bits)><else><bitsetInlineComparison(s, bits)><endif>}; separator=" || ">
 >>
 
-// Java language spec 15.19 - shift operators mask operands rather than overflow to 0... need range test
+// Javascript language spec - shift operators are 32 bits long max
 testShiftInRange(shiftAmount) ::= <<
-((<shiftAmount>) & ~0x3f) == 0
+((<shiftAmount>) & ~0x1f) == 0
 >>
 
 // produces smaller bytecode only when bits.ttypes contains more than two items
diff --git a/tool/src/org/antlr/v4/codegen/JavaScriptTarget.java b/tool/src/org/antlr/v4/codegen/JavaScriptTarget.java
index 68701e284c..28b13d58dc 100644
--- a/tool/src/org/antlr/v4/codegen/JavaScriptTarget.java
+++ b/tool/src/org/antlr/v4/codegen/JavaScriptTarget.java
@@ -41,7 +41,7 @@
 
 /**
  *
- * @author Sam Harwell
+ * @author Eric Vergnaud
  */
 public class JavaScriptTarget extends Target {
 
diff --git a/tool/test/org/antlr/v4/test/rt/js/node/TestBitSetWordSize.java b/tool/test/org/antlr/v4/test/rt/js/node/TestBitSetWordSize.java
new file mode 100644
index 0000000000..b082a73e57
--- /dev/null
+++ b/tool/test/org/antlr/v4/test/rt/js/node/TestBitSetWordSize.java
@@ -0,0 +1,35 @@
+package org.antlr.v4.test.rt.js.node;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class TestBitSetWordSize extends BaseTest {
+
+	@Test
+	public void testBitSetWordSize() throws Exception {
+		StringBuilder sb = new StringBuilder();
+		sb.append("grammar T;\n");
+		// create 40 tokens so we exceed 32 bits size
+		for(int i=1;i<=40;i++) {
+			sb.append("T");
+			sb.append(i);
+			sb.append(" : 'x");
+			sb.append(i);
+			sb.append("';\n");
+		}
+		// create a rule which will generate bit set test
+		sb.append("o : T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8;\n");
+		// create a rule where expected token - 32 uses same bit than optional token
+		sb.append("a : o? T36 {console.log('ok');};\n");
+		sb.append("WS : (' '|'\\n') -> skip ;");
+		String grammar = sb.toString();
+		// use input which triggers bug when word size is 64
+		String input = "x36";
+		String found = execParser("T.g4", grammar, "TParser", "TLexer", "TListener", "TVisitor", "a", input, false);
+		assertEquals("ok\n", found);
+		assertNull(this.stderrDuringParse);
+	}
+
+
+
+}
\ No newline at end of file