diff --git a/photon/libc/sys/horizon/heap.c b/photon/libc/sys/horizon/heap.c
index ce5c076..de9c736 100644
--- a/photon/libc/sys/horizon/heap.c
+++ b/photon/libc/sys/horizon/heap.c
@@ -9,6 +9,9 @@
 #include <magenta/misc.h>
 #include <magenta/vmar.h>
 
+/* 1 GiB */
+#define HEAP_REGION_SZ 0x40000000
+
 #define ROUND_UP(x, b) x += (b) - ((x) % (b))
 
 static uintptr_t heap_start = 0;
@@ -16,17 +19,24 @@ static uintptr_t heap_end = 0;
 static uintptr_t heap_alloc_point = 0;
 static size_t heap_sz = 0;
 static mx_handle_t heap_vmo = MX_NULL_HANDLE;
+static mx_handle_t heap_vmar = MX_NULL_HANDLE;
 
 void __crt_heap_init(size_t sz)
 {
-    mx_status_t status = mx_vmo_create(
+    mx_handle_t root_vmar = mx_bootstrap_handle_get(MX_B_VMAR_ROOT);
+    mx_vaddr_t heap = 0;
+
+    mx_status_t status = mx_vmar_allocate(root_vmar,
+            MX_VM_CAN_MAP_READ | MX_VM_CAN_MAP_WRITE | MX_VM_CAN_MAP_SPECIFIC,
+            0, HEAP_REGION_SZ, &heap_vmar, &heap);
+
+    status = mx_vmo_create(
             sz,
             MX_VM_CAN_MAP_READ | MX_VM_CAN_MAP_WRITE | MX_VM_CAN_MAP_SPECIFIC,
             &heap_vmo);
 
-    mx_vaddr_t heap = 0;
-    mx_vmar_map(mx_bootstrap_handle_get(MX_B_VMAR_ROOT),
-            MX_VM_PERM_READ | MX_VM_PERM_WRITE,
+    mx_vmar_map(heap_vmar,
+            MX_VM_PERM_READ | MX_VM_PERM_WRITE | MX_VM_SPECIFIC,
             0, heap_vmo, 0, sz,
             &heap);
 
@@ -57,10 +67,10 @@ void *__crt_heap_extend(size_t sz)
     mx_vmo_set_size(heap_vmo, heap_sz + sz);
 
     mx_vaddr_t vmar_base, alloc_base;
-    mx_vmar_bounds(mx_bootstrap_handle_get(MX_B_VMAR_ROOT), &vmar_base, NULL);
+    mx_vmar_bounds(heap_vmar, &vmar_base, NULL);
     size_t offset = heap_end - vmar_base;
 
-    mx_status_t err = mx_vmar_map(mx_bootstrap_handle_get(MX_B_VMAR_ROOT),
+    mx_status_t err = mx_vmar_map(heap_vmar,
             MX_VM_PERM_READ | MX_VM_PERM_WRITE | MX_VM_SPECIFIC,
             offset, heap_vmo, heap_sz, sz, &alloc_base);