diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 946777f48b..6d44d0480d 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -1152,6 +1152,10 @@ GetDefaultTablespace(char relpersistence)
 typedef struct
 {
 	int			numSpcs;
+	/*
+	 * InvalidOid stored in the tblSpcs member means use the database default
+	 * tablespace.
+	 */
 	Oid			tblSpcs[FLEXIBLE_ARRAY_MEMBER];
 } temp_tablespaces_extra;
 
@@ -1226,6 +1230,7 @@ check_temp_tablespaces(char **newval, void **extra, GucSource source)
 			 */
 			if (curoid == MyDatabaseTableSpace)
 			{
+				/* The default tablespace is indicated by the value InvalidOid */
 				tblSpcs[numSpcs++] = InvalidOid;
 				continue;
 			}
diff --git a/src/backend/storage/file/sharedfileset.c b/src/backend/storage/file/sharedfileset.c
index d41b39a177..9c412959d8 100644
--- a/src/backend/storage/file/sharedfileset.c
+++ b/src/backend/storage/file/sharedfileset.c
@@ -64,6 +64,20 @@ SharedFileSetInit(SharedFileSet *fileset, dsm_segment *seg)
 		fileset->tablespaces[0] = DEFAULTTABLESPACE_OID;
 		fileset->ntablespaces = 1;
 	}
+	else
+	{
+		int i;
+
+		/*
+		 * Tablespace set to InvalidOid means use the default tablespace for
+		 * the database.
+		 */
+		for (i = 0; i < fileset->ntablespaces; i++)
+		{
+			if (fileset->tablespaces[i] == InvalidOid)
+				fileset->tablespaces[i] = MyDatabaseTableSpace;
+		}
+	}
 
 	/* Register our cleanup callback. */
 	on_dsm_detach(seg, SharedFileSetOnDetach, PointerGetDatum(fileset));