diff --git a/arch/arm/src/cortexm3/up_initialstate.c b/arch/arm/src/cortexm3/up_initialstate.c
index 9bf65bf57a..951ce1a95f 100644
--- a/arch/arm/src/cortexm3/up_initialstate.c
+++ b/arch/arm/src/cortexm3/up_initialstate.c
@@ -110,6 +110,16 @@ void up_initial_state(_TCB *tcb)
 
       xcp->regs[REG_PIC] = (uint32)tcb->dspace->region;
     }
+
+  /* Make certain that bit 0 is set in the main entry address.  This
+   * is only an issue when NXFLAT is enabled.  NXFLAT doesn't know
+   * anything about thumb; the addresses that NXFLAT sets are based
+   * on file header info and won't have bit 0 set.
+   */
+
+#ifdef CONFIG_NXFLAT
+  tcb->entry.main = (main_t)((uint32)tcb->entry.main | 1);
+#endif
 #endif
 
   /* Enable or disable interrupts, based on user configuration */