diff -Nur boost_1_51_0.orig/tools/build/v2/engine/execunix.c boost_1_51_0/tools/build/v2/engine/execunix.c
--- boost_1_51_0.orig/tools/build/v2/engine/execunix.c	2012-06-06 00:00:21.000000000 -0400
+++ boost_1_51_0/tools/build/v2/engine/execunix.c	2012-11-02 23:31:40.362841545 -0400
@@ -392,7 +392,7 @@
 
     /* Compute max read file descriptor for use in select. */
     FD_ZERO(fds);
-    for ( i = 0; i < globs.jobs; ++i )
+    for ( i = 0; i < MAXJOBS && i < globs.jobs; ++i )
     {
         if ( 0 < cmdtab[ i ].fd[ OUT ] )
         {
@@ -473,7 +473,7 @@
 
         if ( 0 < ret )
         {
-            for ( i = 0; i < globs.jobs; ++i )
+            for ( i = 0; i < MAXJOBS && i < globs.jobs; ++i )
             {
                 int out = 0;
                 int err = 0;