diff --git a/sim/ft32/ChangeLog b/sim/ft32/ChangeLog
index 29f661fca23..47218b4e652 100644
--- a/sim/ft32/ChangeLog
+++ b/sim/ft32/ChangeLog
@@ -1,3 +1,7 @@
+2015-09-29  James Bowman  <james.bowman@ftdichip.com>
+
+	* interp.c (cpu_mem_write): Do no write PM when locked.
+
 2015-09-22  James Bowman  <james.bowman@ftdichip.com>
 
 	* ft32/interp.c (cpu_mem_read): Call getchar when ea is 0x10000.
diff --git a/sim/ft32/interp.c b/sim/ft32/interp.c
index a20907c5c86..c769ff7a3be 100644
--- a/sim/ft32/interp.c
+++ b/sim/ft32/interp.c
@@ -205,8 +205,12 @@ static void cpu_mem_write (SIM_DESC sd, uint32_t dw, uint32_t ea, uint32_t d)
 	  cpu->state.pm_addr = d;
 	  break;
 	case 0x1fc88:
-	  /* Write to PM */
-	  ft32_write_item (sd, dw, cpu->state.pm_addr, d);
+	  if (cpu->state.pm_unlock)
+	    {
+	      /* Write to PM.  */
+	      ft32_write_item (sd, dw, cpu->state.pm_addr, d);
+	      cpu->state.pm_addr += 4;
+	    }
 	  break;
 	case 0x1fffc:
 	  /* Normal exit.  */