diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c
index 64eec91..db436e0 100644
--- a/src/backend/executor/nodeHash.c
+++ b/src/backend/executor/nodeHash.c
@@ -29,7 +29,6 @@
 #include "access/htup_details.h"
 #include "access/parallel.h"
 #include "catalog/pg_statistic.h"
-#include "commands/tablespace.h"
 #include "executor/execdebug.h"
 #include "executor/hashjoin.h"
 #include "executor/nodeHash.h"
@@ -570,9 +569,7 @@ ExecHashTableCreate(HashState *state, List *hashOperators, List *hashCollations,
 			palloc0(nbatch * sizeof(BufFile *));
 		hashtable->outerBatchFile = (BufFile **)
 			palloc0(nbatch * sizeof(BufFile *));
-		/* The files will not be opened until needed... */
-		/* ... but make sure we have temp tablespaces established for them */
-		PrepareTempTablespaces();
+		/* The files will not be opened until needed */
 	}
 
 	MemoryContextSwitchTo(oldcxt);
@@ -917,8 +914,6 @@ ExecHashIncreaseNumBatches(HashJoinTable hashtable)
 			palloc0(nbatch * sizeof(BufFile *));
 		hashtable->outerBatchFile = (BufFile **)
 			palloc0(nbatch * sizeof(BufFile *));
-		/* time to establish the temp tablespaces, too */
-		PrepareTempTablespaces();
 	}
 	else
 	{
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index fdac985..da89f2b 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -83,6 +83,7 @@
 #include "access/xact.h"
 #include "access/xlog.h"
 #include "catalog/pg_tablespace.h"
+#include "commands/tablespace.h"
 #include "common/file_perm.h"
 #include "pgstat.h"
 #include "portability/mem.h"
@@ -1466,6 +1467,14 @@ OpenTemporaryFile(bool interXact)
 	File		file = 0;
 
 	/*
+	 * If we want to use a temp tablespace, make sure that info has been set
+	 * up in the current transaction.  (This is harmless if we're not in a
+	 * transaction, and it's also cheap if the info is already set up.)
+	 */
+	if (!interXact)
+		PrepareTempTablespaces();
+
+	/*
 	 * Make sure the current resource owner has space for this File before we
 	 * open it, if we'll be registering it below.
 	 */
@@ -2732,6 +2741,7 @@ GetTempTablespaces(Oid *tableSpaces, int numSpaces)
 Oid
 GetNextTempTableSpace(void)
 {
+	Assert(TempTablespacesAreSet());
 	if (numTempTableSpaces > 0)
 	{
 		/* Advance nextTempTableSpace counter with wraparound */
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 3eebd9e..bd9f215 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -101,7 +101,6 @@
 #include "access/nbtree.h"
 #include "catalog/index.h"
 #include "catalog/pg_am.h"
-#include "commands/tablespace.h"
 #include "executor/executor.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
@@ -2464,13 +2463,6 @@ inittapestate(Tuplesortstate *state, int maxTapes)
 	if (tapeSpace + GetMemoryChunkSpace(state->memtuples) < state->allowedMem)
 		USEMEM(state, tapeSpace);
 
-	/*
-	 * Make sure that the temp file(s) underlying the tape set are created in
-	 * suitable temp tablespaces.  For parallel sorts, this should have been
-	 * called already, but it doesn't matter if it is called a second time.
-	 */
-	PrepareTempTablespaces();
-
 	state->mergeactive = (bool *) palloc0(maxTapes * sizeof(bool));
 	state->tp_fib = (int *) palloc0(maxTapes * sizeof(int));
 	state->tp_runs = (int *) palloc0(maxTapes * sizeof(int));
diff --git a/src/backend/utils/sort/tuplestore.c b/src/backend/utils/sort/tuplestore.c
index 0f38e7c..5c9d977 100644
--- a/src/backend/utils/sort/tuplestore.c
+++ b/src/backend/utils/sort/tuplestore.c
@@ -811,6 +811,9 @@ tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
 			/*
 			 * Nope; time to switch to tape-based operation.  Make sure that
 			 * the temp file(s) are created in suitable temp tablespaces.
+			 * (Note: we could leave it to fd.c to do PrepareTempTablespaces,
+			 * but it seems better to do it here, so that any catalog access
+			 * is done with the caller's resources not the tuplestore's.)
 			 */
 			PrepareTempTablespaces();