Index: class.c
==================================================================
--- class.c
+++ class.c
@@ -830,11 +830,11 @@
           n=0;
           for(;;) {
             nxttok();
             if(tokent==TF_MACRO+TF_CLOSE) break;
             if(tokent!=TF_INT) ParseError("Number expected\n");
-            n|=1<<tokenv;
+            if(tokenv<32) n|=1<<tokenv;
           }
           tokent=TF_INT;
           tokenv=n;
           break;
         case MAC_VERSION:

Index: class.doc
==================================================================
--- class.doc
+++ class.doc
@@ -141,11 +141,12 @@
 {band <numbers...>}
   Bitwise AND. The result is -1 if no arguments are specified.
 
 {bit <numbers...>}
   The numbers are in range 0 to 31 and denote bit positions; the result is
-  a number with only those bits set.
+  a number with only those bits set. If there are any numbers out of range
+  0 to 31 then the numbers out of range are ignored.
 
 {bnot <number>}
   Bitwise complement.
 
 {bor <numbers...>}