diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 38e0de3b03..ac8d4799f3 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -539,9 +539,11 @@ static int __init make_memory_node(const struct domain *d,
     int res, i;
     int reg_size = addrcells + sizecells;
     int nr_cells = reg_size*kinfo->mem.nr_banks;
-    __be32 reg[nr_cells];
+    __be32 reg[NR_MEM_BANKS * 4 /* Worst case addrcells + sizecells */];
     __be32 *cells;
 
+    BUG_ON(nr_cells >= ARRAY_SIZE(reg));
+
     dt_dprintk("Create memory node (reg size %d, nr cells %d)\n",
                reg_size, nr_cells);