diff --git a/std/js/_std/haxe/io/Bytes.hx b/std/js/_std/haxe/io/Bytes.hx
index 2bab2f9f4cb..bf1785c0c2c 100644
--- a/std/js/_std/haxe/io/Bytes.hx
+++ b/std/js/_std/haxe/io/Bytes.hx
@@ -156,7 +156,7 @@ class Bytes {
 
 	public function toHex():String {
 		var s = new StringBuf();
-		var chars = [];
+		var chars:Array<Int> = [];
 		var str = "0123456789abcdef";
 		for (i in 0...str.length)
 			chars.push(str.charCodeAt(i));
diff --git a/tests/unit/src/unit/issues/Issue13003.hx b/tests/unit/src/unit/issues/Issue13003.hx
new file mode 100644
index 00000000000..c12d42fa480
--- /dev/null
+++ b/tests/unit/src/unit/issues/Issue13003.hx
@@ -0,0 +1,40 @@
+package unit.issues;
+
+class Issue13003 extends Test {
+	#if js
+	function test() {
+		eq("Array<Int>", bytesToHexLookupType());
+
+		var bytes = haxe.io.Bytes.alloc(6);
+		for (index => value in [0x00, 0x0F, 0x10, 0x7F, 0x80, 0xFF])
+			bytes.set(index, value);
+		eq("000f107f80ff", bytes.toHex());
+	}
+	#end
+
+	macro static function bytesToHexLookupType() {
+		var bytes = switch haxe.macro.Context.getType("haxe.io.Bytes") {
+			case TInst(type, _):
+				type.get();
+			case type:
+				haxe.macro.Context.error('Expected haxe.io.Bytes to be a class, got ${haxe.macro.TypeTools.toString(type)}', haxe.macro.Context.currentPos());
+		}
+		var toHex = Lambda.find(bytes.fields.get(), field -> field.name == "toHex");
+		if (toHex == null)
+			haxe.macro.Context.error("Could not find haxe.io.Bytes.toHex", bytes.pos);
+
+		var lookupType = null;
+		function visit(expression:haxe.macro.Type.TypedExpr) {
+			switch expression.expr {
+				case TVar(variable, _) if (variable.name == "chars"):
+					lookupType = haxe.macro.TypeTools.toString(variable.t);
+				case _:
+					haxe.macro.TypedExprTools.iter(expression, visit);
+			}
+		}
+		visit(toHex.expr());
+		if (lookupType == null)
+			haxe.macro.Context.error("Could not find the haxe.io.Bytes.toHex lookup table", toHex.pos);
+		return macro $v{lookupType};
+	}
+}