diff --git a/src/include/utils/memutils_internal.h b/src/include/utils/memutils_internal.h
index 9a9f52ef16..f348282a07 100644
--- a/src/include/utils/memutils_internal.h
+++ b/src/include/utils/memutils_internal.h
@@ -74,6 +74,9 @@ extern void SlabCheck(MemoryContext context);
  * MemoryContextMethodID
  *		A unique identifier for each MemoryContext implementation which
  *		indicates the index into the mcxt_methods[] array. See mcxt.c.
+ *		The maximum value for this enum is constrained by
+ *		MEMORY_CONTEXT_METHODID_MASK.  If an enum value higher than that is
+ *		required then MEMORY_CONTEXT_METHODID_BITS will need to be increased.
  */
 typedef enum MemoryContextMethodID
 {
diff --git a/src/include/utils/memutils_memorychunk.h b/src/include/utils/memutils_memorychunk.h
index 685c177b68..2eefc138e3 100644
--- a/src/include/utils/memutils_memorychunk.h
+++ b/src/include/utils/memutils_memorychunk.h
@@ -159,7 +159,7 @@ MemoryChunkSetHdrMask(MemoryChunk *chunk, void *block,
 	Assert((char *) chunk > (char *) block);
 	Assert(blockoffset <= MEMORYCHUNK_MAX_BLOCKOFFSET);
 	Assert(value <= MEMORYCHUNK_MAX_VALUE);
-	Assert(methodid <= MEMORY_CONTEXT_METHODID_MASK);
+	Assert((int) methodid <= MEMORY_CONTEXT_METHODID_MASK);
 
 	chunk->hdrmask = (((uint64) blockoffset) << MEMORYCHUNK_BLOCKOFFSET_BASEBIT) |
 		(((uint64) value) << MEMORYCHUNK_VALUE_BASEBIT) |
@@ -175,7 +175,7 @@ static inline void
 MemoryChunkSetHdrMaskExternal(MemoryChunk *chunk,
 							  MemoryContextMethodID methodid)
 {
-	Assert(methodid <= MEMORY_CONTEXT_METHODID_MASK);
+	Assert((int) methodid <= MEMORY_CONTEXT_METHODID_MASK);
 
 	chunk->hdrmask = MEMORYCHUNK_MAGIC | (((uint64) 1) << MEMORYCHUNK_EXTERNAL_BASEBIT) |
 		methodid;