diff --git a/DCC.cpp b/DCC.cpp
index 433911d..f776b04 100644
--- a/DCC.cpp
+++ b/DCC.cpp
@@ -81,6 +81,11 @@ static void DCC::setFn( int cab, byte functionNumber, bool on) {
 }
 
 void DCC::setAccessory(int address, byte number, bool activate) {
+  // use masks to detect wrong values and do nothing
+  if(address != address & 511)
+    return;
+  if(number != number & 3)
+    return;
   byte b[2];
 
   b[0] = address % 64 + 128;                                     // first byte is of the form 10AAAAAA, where AAAAAA represent 6 least signifcant bits of accessory address
diff --git a/DCCEXParser.cpp b/DCCEXParser.cpp
index 77faf0a..4bfed24 100644
--- a/DCCEXParser.cpp
+++ b/DCCEXParser.cpp
@@ -133,7 +133,8 @@ void DCCEXParser::parse(Print & stream, const char *com) {
         break;
          
     case 'a':       // ACCESSORY <a ADDRESS SUBADDRESS ACTIVATE>
-        DCC::setAccessory(p[0],p[1],p[2]);
+        if(p[2] != p[2] & 1) return;
+        DCC::setAccessory(p[0],p[1],p[2]==1);
         return;
 
     case 'T':       // TURNOUT  <T ...>