diff --git a/arch/powerpc/lib/bootm.c b/arch/powerpc/lib/bootm.c
index 0685a9331c..6702df51a5 100644
--- a/arch/powerpc/lib/bootm.c
+++ b/arch/powerpc/lib/bootm.c
@@ -163,8 +163,8 @@ void arch_lmb_reserve(struct lmb *lmb)
 	sp = get_sp();
 	debug ("## Current stack ends at 0x%08lx\n", sp);
 
-	/* adjust sp by 1K to be safe */
-	sp -= 1024;
+	/* adjust sp by 4K to be safe */
+	sp -= 4096;
 	lmb_reserve(lmb, sp, (CONFIG_SYS_SDRAM_BASE + get_effective_memsize() - sp));
 
 	return ;