diff --git a/scp.c b/scp.c
index a7c66c86..6dc932e3 100644
--- a/scp.c
+++ b/scp.c
@@ -1180,6 +1180,9 @@ static const char simh_help[] =
       "+set clock nocatchup         disable catchup clock ticks\n"
       "+set clock catchup           enable catchup clock ticks\n"
       "+set clock calib=n%%          specify idle calibration skip %%\n"
+      "+set clock stop=n            stop execution after n instructions\n\n"
+      " The set clock stop command allows execution to have a bound when\n"
+      " execution starts with a BOOT, NEXT or CONTINUE command.\n"
 #define HLP_SET_ASYNCH "*Commands SET Asynch"
       "3Asynch\n"
       "+set asynch                  enable asynchronous I/O\n"
@@ -8383,7 +8386,7 @@ CONST char *tptr;
 
 *status = SCPE_OK;
 val = strtotv ((CONST char *)cptr, &tptr, radix);
-if ((cptr == tptr) || ((max > 0) && (val > max)))
+if ((cptr == tptr) || (val > max))
     *status = SCPE_ARG;
 else {
     while (sim_isspace (*tptr)) tptr++;
diff --git a/sim_defs.h b/sim_defs.h
index cee3d42e..7e9dc836 100644
--- a/sim_defs.h
+++ b/sim_defs.h
@@ -231,9 +231,11 @@ typedef unsigned long           t_uint64;
 #if defined (USE_INT64)                                 /* 64b data */
 typedef t_int64         t_svalue;                       /* signed value */
 typedef t_uint64        t_value;                        /* value */
+#define T_VALUE_MAX     0xffffffffffffffffuLL
 #else                                                   /* 32b data */
 typedef int32           t_svalue;
 typedef uint32          t_value;
+#define T_VALUE_MAX     0xffffffffUL
 #endif                                                  /* end 64b data */
 
 #if defined (USE_INT64) && defined (USE_ADDR64)         /* 64b address */
diff --git a/sim_timer.c b/sim_timer.c
index bcbe7010..4159f3a1 100644
--- a/sim_timer.c
+++ b/sim_timer.c
@@ -1313,7 +1313,7 @@ t_value stop_time;
 
 if (cptr == NULL)
     return SCPE_ARG;
-stop_time = get_uint (cptr, 10, 0, &r);
+stop_time = get_uint (cptr, 10, T_VALUE_MAX, &r);
 if (r != SCPE_OK)
     return r;
 if (stop_time <= (t_value)sim_gtime())