diff --git a/photon/libc/malloc/dlmalloc/malloc.c b/photon/libc/malloc/dlmalloc/malloc.c
index 4942e8b..969e6ad 100644
--- a/photon/libc/malloc/dlmalloc/malloc.c
+++ b/photon/libc/malloc/dlmalloc/malloc.c
@@ -242,10 +242,10 @@
 #define LACKS_SYS_PARAM_H
 #define LACKS_SYS_MMAN_H
 
-extern void *__extend_heap(size_t sz);
+extern void *__crt_heap_extend(size_t sz);
 
 #define HAVE_MMAP 0
-#define MORECORE __extend_heap
+#define MORECORE __crt_heap_extend
 #define MORECORE_CONTIGUOUS 1
 
 #endif
diff --git a/photon/libc/sys/magenta/heap.c b/photon/libc/sys/magenta/heap.c
index 04fff00..2b91a29 100644
--- a/photon/libc/sys/magenta/heap.c
+++ b/photon/libc/sys/magenta/heap.c
@@ -1,47 +1,62 @@
-#include <magenta/types.h>
 #include <stdint.h>
 #include <stddef.h>
-#include "__init.h"
-#include "__heap.h"
+#include <string.h>
+#include <sys/handles.h>
+#include <magenta/vmo.h>
+#include <magenta/limits.h>
+#include <magenta/vmar.h>
 
 #define ROUND_UP(x, b) x += (b) - ((x) % (b))
 
 static uintptr_t heap_start = 0;
 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;
 
-int __heap_init()
+void __crt_heap_init(size_t heap_sz)
 {
-#if 0
-    heap_start = (uintptr_t)info->heap_map_base;
-    heap_end = (uintptr_t)info + sizeof(*info);
-    ROUND_UP(heap_end, 0x1000);
-    heap_segment = info->heap;
+    mx_status_t status = mx_vmo_create(
+            heap_sz,
+            MX_VM_CAN_MAP_READ | MX_VM_CAN_MAP_WRITE | MX_VM_CAN_MAP_SPECIFIC,
+            &heap_vmo);
 
-    unsigned long sz = 0;
-    mx_segment_get_size(heap_segment, &sz);
-    heap_sz = sz;
-#endif
+    mx_vaddr_t heap = 0;
+    mx_vmar_map(m_get_handle(M_HND_VMAR_ROOT),
+            MX_VM_PERM_READ | MX_VM_PERM_WRITE,
+            0, heap_vmo, 0, heap_sz,
+            &heap);
 
-    return 0;
+    heap_start = heap;
+    heap_end = heap + heap_sz;
+    heap_alloc_point = heap_start;
 }
 
-void *__extend_heap(size_t sz)
+void *__crt_heap_extend(size_t sz)
 {
-#if 0
-    if (sz == 0) {
-        return (void *)(heap_end + 1);
+    if (!heap_start) {
+        __crt_heap_init(sz);
+        return (void *)heap_start;
     }
 
-    void *start = (void *)heap_start;
+    if (sz % MX_PAGE_SIZE) {
+        sz &= (MX_PAGE_SIZE - 1);
+        sz += MX_PAGE_SIZE;
+    }
 
-    uintptr_t ret = heap_end;
-    mx_segment_set_size(heap_segment, heap_sz + sz);
-    mx_segment_map(heap_segment, 0, heap_sz + sz, &start);
+    mx_vmo_set_size(heap_vmo, heap_sz + sz);
+
+    mx_vaddr_t vmar_base, alloc_base;
+    mx_vmar_bounds(m_get_handle(M_HND_VMAR_ROOT), &vmar_base, NULL);
+    mx_vaddr_t offset = heap_end - vmar_base;
+
+    mx_vmar_map(m_get_handle(M_HND_VMAR_ROOT),
+            MX_VM_PERM_READ | MX_VM_PERM_WRITE | MX_VM_SPECIFIC,
+            offset, heap_vmo, heap_sz, sz, &alloc_base);
     heap_sz += sz;
+
+    void *out = (void *)heap_end;
     heap_end += sz;
-    return (void *)ret;
-#endif
-    return NULL;
+
+    return out;
 }