diff --git a/cafe/coreinit/exports.def b/cafe/coreinit/exports.def
index 5c9c7ec8..dd1aa205 100644
--- a/cafe/coreinit/exports.def
+++ b/cafe/coreinit/exports.def
@@ -242,6 +242,9 @@ MCP_DeleteTitleAsync
 MCP_DeviceList
 MCP_FullDeviceList
 
+// coreinit/memdefaultheap.h
+CoreInitDefaultHeap
+
 // coreinit/memheap.h
 MEMGetArena
 MEMGetBaseHeapHandle
@@ -426,7 +429,7 @@ __os_snprintf
 // ----------------------------------------------------------------------------
 
 :DATA
-// coreinit/defaultheap.h
+// coreinit/memdefaultheap.h
 MEMAllocFromDefaultHeap
 MEMAllocFromDefaultHeapEx
 MEMFreeToDefaultHeap
diff --git a/include/coreinit/memdefaultheap.h b/include/coreinit/memdefaultheap.h
index ac4c2b1a..cbb08787 100644
--- a/include/coreinit/memdefaultheap.h
+++ b/include/coreinit/memdefaultheap.h
@@ -1,5 +1,6 @@
 #pragma once
 #include <wut.h>
+#include "memheap.h"
 
 /**
  * \defgroup coreinit_memdefaultheap Default Heap
@@ -19,6 +20,27 @@ extern MEMAllocFromDefaultHeapFn MEMAllocFromDefaultHeap;
 extern MEMAllocFromDefaultHeapExFn MEMAllocFromDefaultHeapEx;
 extern MEMFreeToDefaultHeapFn MEMFreeToDefaultHeap;
 
+/**
+ * Default implementation of __preinit_user.
+ */
+void
+CoreInitDefaultHeap(MEMHeapHandle *outMem1,
+                    MEMHeapHandle *outFG,
+                    MEMHeapHandle *outMem2);
+
+/**
+ * Allows the user to completely customise the default heaps, this runs after
+ * the rpx code section has loaded but before the data section as the data
+ * sections are allocated from the default heap.
+ *
+ * This is for a user to export from their .rpx file, it is not exported from
+ * coreinit.rpl
+ */
+void
+__preinit_user(MEMHeapHandle *outMem1,
+               MEMHeapHandle *outFG,
+               MEMHeapHandle *outMem2);
+
 #ifdef __cplusplus
 }
 #endif