diff --git a/CodenameOne/src/com/codename1/io/JSONSanitizer.java b/CodenameOne/src/com/codename1/io/JSONSanitizer.java
index 699098b629..31e839d4bb 100644
--- a/CodenameOne/src/com/codename1/io/JSONSanitizer.java
+++ b/CodenameOne/src/com/codename1/io/JSONSanitizer.java
@@ -324,8 +324,10 @@ private static boolean canonicalizeNumber(
                         --nZeroesPending;
                     }
 
-                    // TODO: limit s to 21 digits?
-                    sanitizedJson.setCharAt(digitOutPos++, vdigit);
+                    // Limit s to 21 digits
+                    if (digitOutPos - intStart < 21) {
+                        sanitizedJson.setCharAt(digitOutPos++, vdigit);
+                    }
                 }
             }
         }