diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 22afdc0f90f..90a21a3a789 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -48,6 +48,7 @@
 #include "catalog/pg_type.h"
 #include "catalog/storage.h"
 #include "commands/tablecmds.h"
+#include "commands/event_trigger.h"
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "miscadmin.h"
@@ -191,7 +192,8 @@ relationHasPrimaryKey(Relation rel)
 void
 index_check_primary_key(Relation heapRel,
 						IndexInfo *indexInfo,
-						bool is_alter_table)
+						bool is_alter_table,
+						IndexStmt *stmt)
 {
 	List	   *cmds;
 	int			i;
@@ -263,7 +265,11 @@ index_check_primary_key(Relation heapRel,
 	 * unduly.
 	 */
 	if (cmds)
+	{
+		EventTriggerAlterTableStart((Node *) stmt);
 		AlterTableInternal(RelationGetRelid(heapRel), cmds, false);
+		EventTriggerAlterTableEnd();
+	}
 }
 
 /*
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index d344f97a69a..782cb2d526d 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -1699,11 +1699,6 @@ EventTriggerCollectSimpleCommand(ObjectAddress address,
  * Note we don't collect the command immediately; instead we keep it in
  * currentCommand, and only when we're done processing the subcommands we will
  * add it to the command list.
- *
- * XXX -- this API isn't considering the possibility of an ALTER TABLE command
- * being called reentrantly by an event trigger function.  Do we need stackable
- * commands at this level?	Perhaps at least we should detect the condition and
- * raise an error.
  */
 void
 EventTriggerAlterTableStart(Node *parsetree)
@@ -1728,6 +1723,7 @@ EventTriggerAlterTableStart(Node *parsetree)
 	command->d.alterTable.subcmds = NIL;
 	command->parsetree = copyObject(parsetree);
 
+	command->parent = currentEventTriggerState->currentCommand;
 	currentEventTriggerState->currentCommand = command;
 
 	MemoryContextSwitchTo(oldcxt);
@@ -1768,6 +1764,7 @@ EventTriggerCollectAlterTableSubcmd(Node *subcmd, ObjectAddress address)
 		return;
 
 	Assert(IsA(subcmd, AlterTableCmd));
+	Assert(OidIsValid(currentEventTriggerState->currentCommand));
 	Assert(OidIsValid(currentEventTriggerState->currentCommand->d.alterTable.objectId));
 
 	oldcxt = MemoryContextSwitchTo(currentEventTriggerState->cxt);
@@ -1793,11 +1790,15 @@ EventTriggerCollectAlterTableSubcmd(Node *subcmd, ObjectAddress address)
 void
 EventTriggerAlterTableEnd(void)
 {
+	CollectedCommand *parent;
+
 	/* ignore if event trigger context not set, or collection disabled */
 	if (!currentEventTriggerState ||
 		currentEventTriggerState->commandCollectionInhibited)
 		return;
 
+	parent = currentEventTriggerState->currentCommand->parent;
+
 	/* If no subcommands, don't collect */
 	if (list_length(currentEventTriggerState->currentCommand->d.alterTable.subcmds) != 0)
 	{
@@ -1808,7 +1809,7 @@ EventTriggerAlterTableEnd(void)
 	else
 		pfree(currentEventTriggerState->currentCommand);
 
-	currentEventTriggerState->currentCommand = NULL;
+	currentEventTriggerState->currentCommand = parent;
 }
 
 /*
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index ec9951823e6..756d30c2770 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -31,6 +31,7 @@
 #include "commands/comment.h"
 #include "commands/dbcommands.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/tablecmds.h"
 #include "commands/tablespace.h"
 #include "mb/pg_wchar.h"
@@ -575,7 +576,7 @@ DefineIndex(Oid relationId,
 	 * Extra checks when creating a PRIMARY KEY index.
 	 */
 	if (stmt->primary)
-		index_check_primary_key(rel, indexInfo, is_alter_table);
+		index_check_primary_key(rel, indexInfo, is_alter_table, stmt);
 
 	/*
 	 * We disallow indexes on system columns other than OID.  They would not
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 408aa1d63dc..1894485901d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -6007,7 +6007,7 @@ ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
 
 	/* Extra checks needed if making primary key */
 	if (stmt->primary)
-		index_check_primary_key(rel, indexInfo, true);
+		index_check_primary_key(rel, indexInfo, true, stmt);
 
 	/* Note we currently don't support EXCLUSION constraints here */
 	if (stmt->primary)
diff --git a/src/backend/commands/view.c b/src/backend/commands/view.c
index 7395eeea33f..67046752d30 100644
--- a/src/backend/commands/view.c
+++ b/src/backend/commands/view.c
@@ -61,6 +61,8 @@ validateWithCheckOption(char *value)
  *
  * Create a view relation and use the rules system to store the query
  * for the view.
+ *
+ * EventTriggerAlterTableStart must have been called already.
  *---------------------------------------------------------------------
  */
 static ObjectAddress
@@ -186,6 +188,7 @@ DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
 				atcmds = lappend(atcmds, atcmd);
 			}
 
+			/* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 			AlterTableInternal(viewOid, atcmds, true);
 
 			/* Make the new view columns visible */
@@ -217,6 +220,7 @@ DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
 		atcmd->def = (Node *) options;
 		atcmds = list_make1(atcmd);
 
+		/* EventTriggerAlterTableStart called by ProcessUtilitySlow */
 		AlterTableInternal(viewOid, atcmds, true);
 
 		ObjectAddressSet(address, RelationRelationId, viewOid);
diff --git a/src/include/catalog/index.h b/src/include/catalog/index.h
index 37e6ef3fa93..3fbebd066dc 100644
--- a/src/include/catalog/index.h
+++ b/src/include/catalog/index.h
@@ -40,7 +40,8 @@ typedef enum
 
 extern void index_check_primary_key(Relation heapRel,
 						IndexInfo *indexInfo,
-						bool is_alter_table);
+						bool is_alter_table,
+						IndexStmt *stmt);
 
 extern Oid index_create(Relation heapRelation,
 			 const char *indexRelationName,
diff --git a/src/include/tcop/deparse_utility.h b/src/include/tcop/deparse_utility.h
index 046184d1421..af22c61859e 100644
--- a/src/include/tcop/deparse_utility.h
+++ b/src/include/tcop/deparse_utility.h
@@ -44,6 +44,7 @@ typedef struct CollectedATSubcmd
 typedef struct CollectedCommand
 {
 	CollectedCommandType type;
+
 	bool		in_extension;
 	Node	   *parsetree;
 
@@ -100,6 +101,8 @@ typedef struct CollectedCommand
 			GrantObjectType objtype;
 		}			defprivs;
 	}			d;
+
+	struct CollectedCommand	*parent;		/* when nested */
 } CollectedCommand;
 
 #endif   /* DEPARSE_UTILITY_H */