diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index fc495d6a62..06f5eb003c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1482,7 +1482,7 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,
 	Assert(written == write_len);
 
 	/* Align the end position, so that the next record starts aligned */
-	CurrPos = MAXALIGN(CurrPos);
+	CurrPos = MAXALIGN64(CurrPos);
 
 	/*
 	 * If this was an xlog-switch, it's not enough to write the switch record,
diff --git a/src/include/c.h b/src/include/c.h
index 14bfdcd4da..8916310b5b 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -551,6 +551,18 @@ typedef NameData *Name;
 #define DOUBLEALIGN_DOWN(LEN)	TYPEALIGN_DOWN(ALIGNOF_DOUBLE, (LEN))
 #define MAXALIGN_DOWN(LEN)		TYPEALIGN_DOWN(MAXIMUM_ALIGNOF, (LEN))
 
+/*
+ * The above macros will not work with types wider than intptr_t, like with
+ * uint64 on 32-bit platforms.  That's not problem for the usual use where a
+ * pointer or a length is aligned, but for the odd case that you need to
+ * align something (potentially) wider, use TYPEALIGN64.
+ */
+#define TYPEALIGN64(ALIGNVAL,LEN)  \
+	(((uint64) (LEN) + ((ALIGNVAL) - 1)) & ~((uint64) ((ALIGNVAL) - 1)))
+
+/* we don't currently need wider versions of the other ALIGN macros */
+#define MAXALIGN64(LEN)			TYPEALIGN64(MAXIMUM_ALIGNOF, (LEN))
+
 /* ----------------------------------------------------------------
  *				Section 6:	assertions
  * ----------------------------------------------------------------