diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 96d238c7242..622901a69d5 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/aclchk.c,v 1.140 2007/08/21 01:11:13 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/aclchk.c,v 1.141 2007/10/12 18:55:11 tgl Exp $
  *
  * NOTES
  *	  See acl.h.
@@ -1905,14 +1905,7 @@ pg_tablespace_aclmask(Oid spc_oid, Oid roleid,
 	Acl		   *acl;
 	Oid			ownerId;
 
-	/*
-	 * Only shared relations can be stored in global space; don't let even
-	 * superusers override this
-	 */
-	if (spc_oid == GLOBALTABLESPACE_OID && !IsBootstrapProcessingMode())
-		return 0;
-
-	/* Otherwise, superusers bypass all permission checking. */
+	/* Superusers bypass all permission checking. */
 	if (superuser_arg(roleid))
 		return mask;
 
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index cbf05acfb83..ea985a635dd 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.323 2007/09/08 20:31:14 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.324 2007/10/12 18:55:11 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -43,6 +43,7 @@
 #include "catalog/pg_inherits.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablespace.h"
 #include "catalog/pg_type.h"
 #include "commands/tablecmds.h"
 #include "commands/typecmds.h"
@@ -833,6 +834,25 @@ heap_create_with_catalog(const char *relname,
 							 "with any existing type.")));
 	}
 
+	/*
+	 * Validate shared/non-shared tablespace (must check this before doing
+	 * GetNewRelFileNode, to prevent Assert therein)
+	 */
+	if (shared_relation)
+	{
+		if (reltablespace != GLOBALTABLESPACE_OID)
+			/* elog since this is not a user-facing error */
+			elog(ERROR,
+				 "shared relations must be placed in pg_global tablespace");
+	}
+	else
+	{
+		if (reltablespace == GLOBALTABLESPACE_OID)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("only shared relations can be placed in pg_global tablespace")));
+	}
+
 	/*
 	 * Allocate an OID for the relation, unless we were told what to use.
 	 *
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 8137377e7a5..0e76bc9800d 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.285 2007/09/20 17:56:30 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.286 2007/10/12 18:55:12 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -36,6 +36,7 @@
 #include "catalog/pg_constraint.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_opclass.h"
+#include "catalog/pg_tablespace.h"
 #include "catalog/pg_type.h"
 #include "executor/executor.h"
 #include "miscadmin.h"
@@ -539,6 +540,25 @@ index_create(Oid heapRelationId,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("shared indexes cannot be created after initdb")));
 
+	/*
+	 * Validate shared/non-shared tablespace (must check this before doing
+	 * GetNewRelFileNode, to prevent Assert therein)
+	 */
+	if (shared_relation)
+	{
+		if (tableSpaceId != GLOBALTABLESPACE_OID)
+			/* elog since this is not a user-facing error */
+			elog(ERROR,
+				 "shared relations must be placed in pg_global tablespace");
+	}
+	else
+	{
+		if (tableSpaceId == GLOBALTABLESPACE_OID)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("only shared relations can be placed in pg_global tablespace")));
+	}
+
 	if (get_relname_relid(indexRelationName, namespaceId))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_TABLE),
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 094f51b5cc9..434e9838947 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.199 2007/09/28 22:25:49 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.200 2007/10/12 18:55:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -302,6 +302,12 @@ createdb(const CreatedbStmt *stmt)
 			aclcheck_error(aclresult, ACL_KIND_TABLESPACE,
 						   tablespacename);
 
+		/* pg_global must never be the default tablespace */
+		if (dst_deftablespace == GLOBALTABLESPACE_OID)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("pg_global cannot be used as default tablespace")));
+
 		/*
 		 * If we are trying to change the default tablespace of the template,
 		 * we require that the template not have any files in the new default
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ea8d7f60898..0af90cb4ac6 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.233 2007/09/29 17:18:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.234 2007/10/12 18:55:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,7 @@
 #include "catalog/pg_inherits.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_opclass.h"
+#include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "catalog/toasting.h"
@@ -5824,6 +5825,12 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace)
 				 errmsg("cannot move system relation \"%s\"",
 						RelationGetRelationName(rel))));
 
+	/* Can't move a non-shared relation into pg_global */
+	if (newTableSpace == GLOBALTABLESPACE_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("only shared relations can be placed in pg_global tablespace")));
+
 	/*
 	 * Don't allow moving temp tables of other backends ... their local buffer
 	 * manager is not going to cope.