diff --git a/telephony/java/com/android/internal/telephony/gsm/GsmSmsCbMessage.java b/telephony/java/com/android/internal/telephony/gsm/GsmSmsCbMessage.java
index c3d490a6d5cfa..c15a8004b18cd 100644
--- a/telephony/java/com/android/internal/telephony/gsm/GsmSmsCbMessage.java
+++ b/telephony/java/com/android/internal/telephony/gsm/GsmSmsCbMessage.java
@@ -215,7 +215,7 @@ public class GsmSmsCbMessage {
     private static Pair<Integer, List<Geometry>> parseWarningAreaCoordinates(
             byte[] pdu, int wacOffset) {
         // little-endian
-        int wacDataLength = (pdu[wacOffset + 1] << 8) | pdu[wacOffset];
+        int wacDataLength = ((pdu[wacOffset + 1] & 0xff) << 8) | (pdu[wacOffset] & 0xff);
         int offset = wacOffset + 2;
 
         if (offset + wacDataLength > pdu.length) {