diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 07e2037e9b..99588a330d 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -994,8 +994,21 @@ void free_init_memory(void)
 {
     paddr_t pa = virt_to_maddr(__init_begin);
     unsigned long len = __init_end - __init_begin;
+    uint32_t insn;
+    unsigned int i, nr = len / sizeof(insn);
+    uint32_t *p;
+
     set_pte_flags_on_range(__init_begin, len, mg_rw);
-    memset(__init_begin, 0xcc, len);
+#ifdef CONFIG_ARM_32
+    /* udf instruction i.e (see A8.8.247 in ARM DDI 0406C.c) */
+    insn = 0xe7f000f0;
+#else
+    insn = AARCH64_BREAK_FAULT;
+#endif
+    p = (uint32_t *)__init_begin;
+    for ( i = 0; i < nr; i++ )
+        *(p + i) = insn;
+
     set_pte_flags_on_range(__init_begin, len, mg_clear);
     init_domheap_pages(pa, pa + len);
     printk("Freed %ldkB init memory.\n", (long)(__init_end-__init_begin)>>10);
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 47b910d1eb..ddef59537b 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -221,3 +221,9 @@ SECTIONS
  * code running on the boot time identity map cannot cross a section boundary.
  */
 ASSERT( _end_boot - start <= PAGE_SIZE, "Boot code is larger than 4K")
+/*
+ * __init_[begin|end] MUST be at word size boundary otherwise we cannot
+ * write fault instructions in the space properly.
+ */
+ASSERT(IS_ALIGNED(__init_begin,     4), "__init_begin is misaligned")
+ASSERT(IS_ALIGNED(__init_end,       4), "__init_end is misaligned")