diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 7bbfabe0ea..d52bd2c073 100644
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -466,10 +466,10 @@ MemoryContextIsEmpty(MemoryContext context)
  * Find the memory allocated to blocks for this memory context. If recurse is
  * true, also include children.
  */
-int64
+Size
 MemoryContextMemAllocated(MemoryContext context, bool recurse)
 {
-	int64 total = context->mem_allocated;
+	Size	total = context->mem_allocated;
 
 	AssertArg(MemoryContextIsValid(context));
 
diff --git a/src/include/utils/memutils.h b/src/include/utils/memutils.h
index 6a837bc990..106c83da45 100644
--- a/src/include/utils/memutils.h
+++ b/src/include/utils/memutils.h
@@ -82,7 +82,7 @@ extern void MemoryContextSetParent(MemoryContext context,
 extern Size GetMemoryChunkSpace(void *pointer);
 extern MemoryContext MemoryContextGetParent(MemoryContext context);
 extern bool MemoryContextIsEmpty(MemoryContext context);
-extern int64 MemoryContextMemAllocated(MemoryContext context, bool recurse);
+extern Size MemoryContextMemAllocated(MemoryContext context, bool recurse);
 extern void MemoryContextStats(MemoryContext context);
 extern void MemoryContextStatsDetail(MemoryContext context, int max_children);
 extern void MemoryContextAllowInCriticalSection(MemoryContext context,