diff --git a/exec.c b/exec.c
index 6d7f600c0c..93128fd19a 100644
--- a/exec.c
+++ b/exec.c
@@ -153,7 +153,7 @@ typedef struct subpage_t {
     MemoryRegion iomem;
     AddressSpace *as;
     hwaddr base;
-    uint16_t sub_section[TARGET_PAGE_SIZE];
+    uint16_t sub_section[];
 } subpage_t;
 
 #define PHYS_SECTION_UNASSIGNED 0
@@ -2215,8 +2215,7 @@ static subpage_t *subpage_init(AddressSpace *as, hwaddr base)
 {
     subpage_t *mmio;
 
-    mmio = g_malloc0(sizeof(subpage_t));
-
+    mmio = g_malloc0(sizeof(subpage_t) + TARGET_PAGE_SIZE * sizeof(uint16_t));
     mmio->as = as;
     mmio->base = base;
     memory_region_init_io(&mmio->iomem, NULL, &subpage_ops, mmio,