diff --git a/contrib/hstore/hstore_io.c b/contrib/hstore/hstore_io.c
index 079f662748..7d8986708f 100644
--- a/contrib/hstore/hstore_io.c
+++ b/contrib/hstore/hstore_io.c
@@ -747,7 +747,7 @@ typedef struct RecordIOData
 	Oid			record_type;
 	int32		record_typmod;
 	int			ncolumns;
-	ColumnIOData columns[1];	/* VARIABLE LENGTH ARRAY */
+	ColumnIOData columns[FLEXIBLE_ARRAY_MEMBER];
 } RecordIOData;
 
 PG_FUNCTION_INFO_V1(hstore_from_record);
@@ -805,8 +805,8 @@ hstore_from_record(PG_FUNCTION_ARGS)
 	{
 		fcinfo->flinfo->fn_extra =
 			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
-							   sizeof(RecordIOData) - sizeof(ColumnIOData)
-							   + ncolumns * sizeof(ColumnIOData));
+							   offsetof(RecordIOData, columns) +
+							   ncolumns * sizeof(ColumnIOData));
 		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
 		my_extra->record_type = InvalidOid;
 		my_extra->record_typmod = 0;
@@ -816,8 +816,8 @@ hstore_from_record(PG_FUNCTION_ARGS)
 		my_extra->record_typmod != tupTypmod)
 	{
 		MemSet(my_extra, 0,
-			   sizeof(RecordIOData) - sizeof(ColumnIOData)
-			   + ncolumns * sizeof(ColumnIOData));
+			   offsetof(RecordIOData, columns) +
+			   ncolumns * sizeof(ColumnIOData));
 		my_extra->record_type = tupType;
 		my_extra->record_typmod = tupTypmod;
 		my_extra->ncolumns = ncolumns;
@@ -990,8 +990,8 @@ hstore_populate_record(PG_FUNCTION_ARGS)
 	{
 		fcinfo->flinfo->fn_extra =
 			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
-							   sizeof(RecordIOData) - sizeof(ColumnIOData)
-							   + ncolumns * sizeof(ColumnIOData));
+							   offsetof(RecordIOData, columns) +
+							   ncolumns * sizeof(ColumnIOData));
 		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
 		my_extra->record_type = InvalidOid;
 		my_extra->record_typmod = 0;
@@ -1001,8 +1001,8 @@ hstore_populate_record(PG_FUNCTION_ARGS)
 		my_extra->record_typmod != tupTypmod)
 	{
 		MemSet(my_extra, 0,
-			   sizeof(RecordIOData) - sizeof(ColumnIOData)
-			   + ncolumns * sizeof(ColumnIOData));
+			   offsetof(RecordIOData, columns) +
+			   ncolumns * sizeof(ColumnIOData));
 		my_extra->record_type = tupType;
 		my_extra->record_typmod = tupTypmod;
 		my_extra->ncolumns = ncolumns;
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 3688163d91..a8cdeaa393 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -216,7 +216,7 @@ typedef struct RecordIOData
 	Oid			record_type;
 	int32		record_typmod;
 	int			ncolumns;
-	ColumnIOData columns[1];	/* VARIABLE LENGTH ARRAY */
+	ColumnIOData columns[FLEXIBLE_ARRAY_MEMBER];
 } RecordIOData;
 
 /* state for populate_recordset */
@@ -2148,8 +2148,8 @@ populate_record_worker(FunctionCallInfo fcinfo, const char *funcname,
 	{
 		fcinfo->flinfo->fn_extra =
 			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
-							   sizeof(RecordIOData) - sizeof(ColumnIOData)
-							   + ncolumns * sizeof(ColumnIOData));
+							   offsetof(RecordIOData, columns) +
+							   ncolumns * sizeof(ColumnIOData));
 		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
 		my_extra->record_type = InvalidOid;
 		my_extra->record_typmod = 0;
@@ -2161,8 +2161,8 @@ populate_record_worker(FunctionCallInfo fcinfo, const char *funcname,
 							my_extra->record_typmod != tupTypmod))
 	{
 		MemSet(my_extra, 0,
-			   sizeof(RecordIOData) - sizeof(ColumnIOData)
-			   + ncolumns * sizeof(ColumnIOData));
+			   offsetof(RecordIOData, columns) +
+			   ncolumns * sizeof(ColumnIOData));
 		my_extra->record_type = tupType;
 		my_extra->record_typmod = tupTypmod;
 		my_extra->ncolumns = ncolumns;
@@ -2653,8 +2653,8 @@ populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
 	{
 		fcinfo->flinfo->fn_extra =
 			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
-							   sizeof(RecordIOData) - sizeof(ColumnIOData)
-							   + ncolumns * sizeof(ColumnIOData));
+							   offsetof(RecordIOData, columns) +
+							   ncolumns * sizeof(ColumnIOData));
 		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
 		my_extra->record_type = InvalidOid;
 		my_extra->record_typmod = 0;
@@ -2664,8 +2664,8 @@ populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
 		my_extra->record_typmod != tupTypmod)
 	{
 		MemSet(my_extra, 0,
-			   sizeof(RecordIOData) - sizeof(ColumnIOData)
-			   + ncolumns * sizeof(ColumnIOData));
+			   offsetof(RecordIOData, columns) +
+			   ncolumns * sizeof(ColumnIOData));
 		my_extra->record_type = tupType;
 		my_extra->record_typmod = tupTypmod;
 		my_extra->ncolumns = ncolumns;