diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c
index 140b0c74d97..9e321283e59 100644
--- a/src/backend/utils/mmgr/aset.c
+++ b/src/backend/utils/mmgr/aset.c
@@ -128,7 +128,7 @@ typedef void *AllocPointer;
 /*
  * AllocSetContext is our standard implementation of MemoryContext.
  *
- * Note: isReset means there is nothing for AllocSetReset to do.  This is
+ * Note: header.isReset means there is nothing for AllocSetReset to do.  This is
  * different from the aset being physically empty (empty blocks list) because
  * we may still have a keeper block.  It's also different from the set being
  * logically empty, because we don't attempt to detect pfree'ing the last
@@ -140,7 +140,6 @@ typedef struct AllocSetContext
 	/* Info about storage allocated in this context: */
 	AllocBlock	blocks;			/* head of list of blocks in this set */
 	AllocChunk	freelist[ALLOCSET_NUM_FREELISTS];		/* free chunk lists */
-	bool		isReset;		/* T = no space alloced since last reset */
 	/* Allocation parameters for this context: */
 	Size		initBlockSize;	/* initial block size */
 	Size		maxBlockSize;	/* maximum block size */
@@ -427,8 +426,6 @@ AllocSetContextCreate(MemoryContext parent,
 		context->keeper = block;
 	}
 
-	context->isReset = true;
-
 	return (MemoryContext) context;
 }
 
@@ -472,10 +469,6 @@ AllocSetReset(MemoryContext context)
 
 	AssertArg(AllocSetIsValid(set));
 
-	/* Nothing to do if no pallocs since startup or last reset */
-	if (set->isReset)
-		return;
-
 #ifdef MEMORY_CONTEXT_CHECKING
 	/* Check for corruption and leaks before freeing */
 	AllocSetCheck(context);
@@ -519,8 +512,6 @@ AllocSetReset(MemoryContext context)
 
 	/* Reset block size allocation sequence, too */
 	set->nextBlockSize = set->initBlockSize;
-
-	set->isReset = true;
 }
 
 /*
@@ -629,8 +620,6 @@ AllocSetAlloc(MemoryContext context, Size size)
 			set->blocks = block;
 		}
 
-		set->isReset = false;
-
 		AllocAllocInfo(set, chunk);
 		return AllocChunkGetPointer(chunk);
 	}
@@ -662,9 +651,6 @@ AllocSetAlloc(MemoryContext context, Size size)
 		randomize_mem((char *) AllocChunkGetPointer(chunk), size);
 #endif
 
-		/* isReset must be false already */
-		Assert(!set->isReset);
-
 		AllocAllocInfo(set, chunk);
 		return AllocChunkGetPointer(chunk);
 	}
@@ -822,8 +808,6 @@ AllocSetAlloc(MemoryContext context, Size size)
 	randomize_mem((char *) AllocChunkGetPointer(chunk), size);
 #endif
 
-	set->isReset = false;
-
 	AllocAllocInfo(set, chunk);
 	return AllocChunkGetPointer(chunk);
 }
@@ -922,9 +906,6 @@ AllocSetRealloc(MemoryContext context, void *pointer, Size size)
 				 set->header.name, chunk);
 #endif
 
-	/* isReset must be false already */
-	Assert(!set->isReset);
-
 	/*
 	 * Chunk sizes are aligned to power of 2 in AllocSetAlloc(). Maybe the
 	 * allocated area already is >= the new size.  (In particular, we always
@@ -1059,15 +1040,13 @@ AllocSetGetChunkSpace(MemoryContext context, void *pointer)
 static bool
 AllocSetIsEmpty(MemoryContext context)
 {
-	AllocSet	set = (AllocSet) context;
-
 	/*
 	 * For now, we say "empty" only if the context is new or just reset. We
 	 * could examine the freelists to determine if all space has been freed,
 	 * but it's not really worth the trouble for present uses of this
 	 * functionality.
 	 */
-	if (set->isReset)
+	if (context->isReset)
 		return true;
 	return false;
 }
diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 8783edf0263..980cce518cf 100644
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -127,7 +127,12 @@ MemoryContextReset(MemoryContext context)
 	if (context->firstchild != NULL)
 		MemoryContextResetChildren(context);
 
-	(*context->methods->reset) (context);
+	/* Nothing to do if no pallocs since startup or last reset */
+	if (!context->isReset)
+	{
+		(*context->methods->reset) (context);
+		context->isReset = true;
+	}
 }
 
 /*
@@ -476,6 +481,7 @@ MemoryContextCreate(NodeTag tag, Size size,
 	node->parent = NULL;		/* for the moment */
 	node->firstchild = NULL;
 	node->nextchild = NULL;
+	node->isReset = true;
 	node->name = ((char *) node) + size;
 	strcpy(node->name, name);
 
@@ -504,13 +510,16 @@ MemoryContextCreate(NodeTag tag, Size size,
 void *
 MemoryContextAlloc(MemoryContext context, Size size)
 {
+	void	   *ret;
 	AssertArg(MemoryContextIsValid(context));
 
 	if (!AllocSizeIsValid(size))
 		elog(ERROR, "invalid memory alloc request size %lu",
 			 (unsigned long) size);
 
-	return (*context->methods->alloc) (context, size);
+	ret = (*context->methods->alloc) (context, size);
+	context->isReset = false;
+	return ret;
 }
 
 /*
@@ -535,6 +544,7 @@ MemoryContextAllocZero(MemoryContext context, Size size)
 
 	MemSetAligned(ret, 0, size);
 
+	context->isReset = false;
 	return ret;
 }
 
@@ -560,6 +570,7 @@ MemoryContextAllocZeroAligned(MemoryContext context, Size size)
 
 	MemSetLoop(ret, 0, size);
 
+	context->isReset = false;
 	return ret;
 }
 
@@ -620,6 +631,9 @@ repalloc(void *pointer, Size size)
 		elog(ERROR, "invalid memory alloc request size %lu",
 			 (unsigned long) size);
 
+	/* isReset must be false already */
+	Assert(!header->context->isReset);
+
 	return (*header->context->methods->realloc) (header->context,
 												 pointer, size);
 }
diff --git a/src/include/nodes/memnodes.h b/src/include/nodes/memnodes.h
index b62ed8f904a..62a0f9730ed 100644
--- a/src/include/nodes/memnodes.h
+++ b/src/include/nodes/memnodes.h
@@ -59,6 +59,7 @@ typedef struct MemoryContextData
 	MemoryContext firstchild;	/* head of linked list of children */
 	MemoryContext nextchild;	/* next child of same parent */
 	char	   *name;			/* context name (just for debugging) */
+	bool		isReset;		/* T = no space alloced since last reset */
 } MemoryContextData;
 
 /* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */