diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 116de1175b..ce1417b8f0 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -3453,6 +3453,9 @@ AbortCurrentTransaction(void)
  *	could issue more commands and possibly cause a failure after the statement
  *	completes).  Subtransactions are verboten too.
  *
+ *	We must also set XACT_FLAGS_NEEDIMMEDIATECOMMIT in MyXactFlags, to ensure
+ *	that postgres.c follows through by committing after the statement is done.
+ *
  *	isTopLevel: passed down from ProcessUtility to determine whether we are
  *	inside a function.  (We will always fail if this is false, but it's
  *	convenient to centralize the check here instead of making callers do it.)
@@ -3494,7 +3497,9 @@ PreventInTransactionBlock(bool isTopLevel, const char *stmtType)
 	if (CurrentTransactionState->blockState != TBLOCK_DEFAULT &&
 		CurrentTransactionState->blockState != TBLOCK_STARTED)
 		elog(FATAL, "cannot prevent transaction chain");
-	/* all okay */
+
+	/* All okay.  Set the flag to make sure the right thing happens later. */
+	MyXactFlags |= XACT_FLAGS_NEEDIMMEDIATECOMMIT;
 }
 
 /*
@@ -3591,6 +3596,13 @@ IsInTransactionBlock(bool isTopLevel)
 		CurrentTransactionState->blockState != TBLOCK_STARTED)
 		return true;
 
+	/*
+	 * If we tell the caller we're not in a transaction block, then inform
+	 * postgres.c that it had better commit when the statement is done.
+	 * Otherwise our report could be a lie.
+	 */
+	MyXactFlags |= XACT_FLAGS_NEEDIMMEDIATECOMMIT;
+
 	return false;
 }
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 6f18b68856..320bbe2b1e 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -2092,32 +2092,16 @@ exec_execute_message(const char *portal_name, long max_rows)
 
 	/*
 	 * We must copy the sourceText and prepStmtName into MessageContext in
-	 * case the portal is destroyed during finish_xact_command. Can avoid the
-	 * copy if it's not an xact command, though.
+	 * case the portal is destroyed during finish_xact_command.  We do not
+	 * make a copy of the portalParams though, preferring to just not print
+	 * them in that case.
 	 */
-	if (is_xact_command)
-	{
-		sourceText = pstrdup(portal->sourceText);
-		if (portal->prepStmtName)
-			prepStmtName = pstrdup(portal->prepStmtName);
-		else
-			prepStmtName = "<unnamed>";
-
-		/*
-		 * An xact command shouldn't have any parameters, which is a good
-		 * thing because they wouldn't be around after finish_xact_command.
-		 */
-		portalParams = NULL;
-	}
+	sourceText = pstrdup(portal->sourceText);
+	if (portal->prepStmtName)
+		prepStmtName = pstrdup(portal->prepStmtName);
 	else
-	{
-		sourceText = portal->sourceText;
-		if (portal->prepStmtName)
-			prepStmtName = portal->prepStmtName;
-		else
-			prepStmtName = "<unnamed>";
-		portalParams = portal->portalParams;
-	}
+		prepStmtName = "<unnamed>";
+	portalParams = portal->portalParams;
 
 	/*
 	 * Report query to various monitoring facilities.
@@ -2216,13 +2200,30 @@ exec_execute_message(const char *portal_name, long max_rows)
 
 	if (completed)
 	{
-		if (is_xact_command)
+		if (is_xact_command || (MyXactFlags & XACT_FLAGS_NEEDIMMEDIATECOMMIT))
 		{
 			/*
 			 * If this was a transaction control statement, commit it.  We
 			 * will start a new xact command for the next command (if any).
+			 * Likewise if the statement required immediate commit.
+			 *
+			 * Note: the reason exec_simple_query() doesn't need to check
+			 * XACT_FLAGS_NEEDIMMEDIATECOMMIT is that it always does
+			 * finish_xact_command() at the end of the query string, and the
+			 * implicit-transaction-block mechanism prevents grouping such
+			 * statements into multi-query strings.  In extended query
+			 * protocol, we ordinarily wouldn't force commit until Sync is
+			 * received, which creates a hazard if the client tries to
+			 * pipeline such statements.
 			 */
 			finish_xact_command();
+
+			/*
+			 * These commands typically don't have any parameters, and even if
+			 * one did we couldn't print them now because the storage went
+			 * away during finish_xact_command.  So pretend there were none.
+			 */
+			portalParams = NULL;
 		}
 		else
 		{
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index 7d2b35213d..300baae120 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -107,6 +107,12 @@ extern PGDLLIMPORT int MyXactFlags;
  */
 #define XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK	(1U << 1)
 
+/*
+ * XACT_FLAGS_NEEDIMMEDIATECOMMIT - records whether the top level statement
+ * is one that requires immediate commit, such as CREATE DATABASE.
+ */
+#define XACT_FLAGS_NEEDIMMEDIATECOMMIT			(1U << 2)
+
 /*
  *	start- and end-of-transaction callbacks for dynamically loaded modules
  */