diff --git a/src/backend/utils/mmgr/mcxt.c b/src/backend/utils/mmgr/mcxt.c
index 64bcc7ef32..3d80abbfae 100644
--- a/src/backend/utils/mmgr/mcxt.c
+++ b/src/backend/utils/mmgr/mcxt.c
@@ -482,6 +482,15 @@ MemoryContextAllowInCriticalSection(MemoryContext context, bool allow)
 MemoryContext
 GetMemoryChunkContext(void *pointer)
 {
+	/*
+	 * Try to detect bogus pointers handed to us, poorly though we can.
+	 * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
+	 * allocated chunk.
+	 */
+	Assert(pointer != NULL);
+	Assert(pointer == (void *) MAXALIGN(pointer));
+	/* adding further Asserts here? See pre-checks in MemoryContextContains */
+
 	return MCXT_METHOD(pointer, get_chunk_context) (pointer);
 }
 
@@ -809,11 +818,10 @@ MemoryContextCheck(MemoryContext context)
  *		Detect whether an allocated chunk of memory belongs to a given
  *		context or not.
  *
- * Caution: this test is reliable as long as 'pointer' does point to
- * a chunk of memory allocated from *some* context.  If 'pointer' points
- * at memory obtained in some other way, there is a small chance of a
- * false-positive result, since the bits right before it might look like
- * a valid chunk header by chance.
+ * Caution: 'pointer' must point to a pointer which was allocated by a
+ * MemoryContext.  It's not safe or valid to use this function on arbitrary
+ * pointers as obtaining the MemoryContext which 'pointer' belongs to requires
+ * possibly several pointer dereferences.
  */
 bool
 MemoryContextContains(MemoryContext context, void *pointer)
@@ -821,9 +829,8 @@ MemoryContextContains(MemoryContext context, void *pointer)
 	MemoryContext ptr_context;
 
 	/*
-	 * NB: Can't use GetMemoryChunkContext() here - that performs assertions
-	 * that aren't acceptable here since we might be passed memory not
-	 * allocated by any memory context.
+	 * NB: We must perform run-time checks here which GetMemoryChunkContext()
+	 * does as assertions before calling GetMemoryChunkContext().
 	 *
 	 * Try to detect bogus pointers handed to us, poorly though we can.
 	 * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
@@ -835,7 +842,7 @@ MemoryContextContains(MemoryContext context, void *pointer)
 	/*
 	 * OK, it's probably safe to look at the context.
 	 */
-	ptr_context = *(MemoryContext *) (((char *) pointer) - sizeof(void *));
+	ptr_context = GetMemoryChunkContext(pointer);
 
 	return ptr_context == context;
 }
@@ -953,6 +960,8 @@ MemoryContextAlloc(MemoryContext context, Size size)
 
 	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -991,6 +1000,8 @@ MemoryContextAllocZero(MemoryContext context, Size size)
 
 	MemSetAligned(ret, 0, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1029,6 +1040,8 @@ MemoryContextAllocZeroAligned(MemoryContext context, Size size)
 
 	MemSetLoop(ret, 0, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1070,6 +1083,8 @@ MemoryContextAllocExtended(MemoryContext context, Size size, int flags)
 	if ((flags & MCXT_ALLOC_ZERO) != 0)
 		MemSetAligned(ret, 0, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1153,6 +1168,8 @@ palloc(Size size)
 
 	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1186,6 +1203,8 @@ palloc0(Size size)
 
 	MemSetAligned(ret, 0, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1225,6 +1244,8 @@ palloc_extended(Size size, int flags)
 	if ((flags & MCXT_ALLOC_ZERO) != 0)
 		MemSetAligned(ret, 0, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1278,6 +1299,8 @@ repalloc(void *pointer, Size size)
 
 	VALGRIND_MEMPOOL_CHANGE(context, pointer, ret, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1313,6 +1336,8 @@ MemoryContextAllocHuge(MemoryContext context, Size size)
 
 	VALGRIND_MEMPOOL_ALLOC(context, ret, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }
 
@@ -1352,6 +1377,8 @@ repalloc_huge(void *pointer, Size size)
 
 	VALGRIND_MEMPOOL_CHANGE(context, pointer, ret, size);
 
+	Assert(MemoryContextContains(context, ret));
+
 	return ret;
 }