diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 42e94971741..2caa84a1253 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1434,7 +1434,7 @@ The commands accepted in walsender mode are:
   </varlistentry>
 
   <varlistentry>
-    <term>CREATE_REPLICATION_SLOT <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }
+    <term>CREATE_REPLICATION_SLOT <replaceable class="parameter">slot_name</> { <literal>PHYSICAL</> [ RESERVE_WAL ] | <literal>LOGICAL</> <replaceable class="parameter">output_plugin</> }
      <indexterm><primary>CREATE_REPLICATION_SLOT</primary></indexterm>
     </term>
     <listitem>
@@ -1463,6 +1463,17 @@ The commands accepted in walsender mode are:
          </para>
        </listitem>
       </varlistentry>
+
+      <varlistentry>
+       <term><literal>RESERVE_WAL</></term>
+       <listitem>
+        <para>
+         Specify that this physical replication reserves <acronym>WAL</>
+         immediately; otherwise <acronym>WAL</> is only reserved upon
+         connection from a streaming replication client.
+        </para>
+       </listitem>
+      </varlistentry>
      </variablelist>
     </listitem>
   </varlistentry>
diff --git a/src/backend/replication/repl_gram.y b/src/backend/replication/repl_gram.y
index e9177ca0db6..1b753644223 100644
--- a/src/backend/replication/repl_gram.y
+++ b/src/backend/replication/repl_gram.y
@@ -76,6 +76,7 @@ Node *replication_parse_result;
 %token K_PHYSICAL
 %token K_LOGICAL
 %token K_SLOT
+%token K_RESERVE_WAL
 
 %type <node>	command
 %type <node>	base_backup start_replication start_logical_replication
@@ -88,6 +89,7 @@ Node *replication_parse_result;
 %type <defelt>	plugin_opt_elem
 %type <node>	plugin_opt_arg
 %type <str>		opt_slot
+%type <boolval>	opt_reserve_wal
 
 %%
 
@@ -181,13 +183,14 @@ base_backup_opt:
 			;
 
 create_replication_slot:
-			/* CREATE_REPLICATION_SLOT slot PHYSICAL */
-			K_CREATE_REPLICATION_SLOT IDENT K_PHYSICAL
+			/* CREATE_REPLICATION_SLOT slot PHYSICAL RESERVE_WAL */
+			K_CREATE_REPLICATION_SLOT IDENT K_PHYSICAL opt_reserve_wal
 				{
 					CreateReplicationSlotCmd *cmd;
 					cmd = makeNode(CreateReplicationSlotCmd);
 					cmd->kind = REPLICATION_KIND_PHYSICAL;
 					cmd->slotname = $2;
+					cmd->reserve_wal = $4;
 					$$ = (Node *) cmd;
 				}
 			/* CREATE_REPLICATION_SLOT slot LOGICAL plugin */
@@ -268,6 +271,11 @@ opt_physical:
 			| /* EMPTY */
 			;
 
+opt_reserve_wal:
+			K_RESERVE_WAL					{ $$ = true; }
+			| /* EMPTY */					{ $$ = false; }
+			;
+
 opt_slot:
 			K_SLOT IDENT
 				{ $$ = $2; }
diff --git a/src/backend/replication/repl_scanner.l b/src/backend/replication/repl_scanner.l
index 91bac21b06b..126e7d90640 100644
--- a/src/backend/replication/repl_scanner.l
+++ b/src/backend/replication/repl_scanner.l
@@ -95,6 +95,7 @@ CREATE_REPLICATION_SLOT		{ return K_CREATE_REPLICATION_SLOT; }
 DROP_REPLICATION_SLOT		{ return K_DROP_REPLICATION_SLOT; }
 TIMELINE_HISTORY	{ return K_TIMELINE_HISTORY; }
 PHYSICAL			{ return K_PHYSICAL; }
+RESERVE_WAL			{ return K_RESERVE_WAL; }
 LOGICAL				{ return K_LOGICAL; }
 SLOT				{ return K_SLOT; }
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 27de156b1ff..c95fe75a721 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -826,6 +826,14 @@ CreateReplicationSlot(CreateReplicationSlotCmd *cmd)
 
 		ReplicationSlotPersist();
 	}
+	else if (cmd->kind == REPLICATION_KIND_PHYSICAL && cmd->reserve_wal)
+	{
+		ReplicationSlotReserveWal();
+
+		/* Write this slot to disk */
+		ReplicationSlotMarkDirty();
+		ReplicationSlotSave();
+	}
 
 	slot_name = NameStr(MyReplicationSlot->data.name);
 	snprintf(xpos, sizeof(xpos), "%X/%X",
diff --git a/src/include/nodes/replnodes.h b/src/include/nodes/replnodes.h
index cac64198508..4e35be6a286 100644
--- a/src/include/nodes/replnodes.h
+++ b/src/include/nodes/replnodes.h
@@ -55,6 +55,7 @@ typedef struct CreateReplicationSlotCmd
 	char	   *slotname;
 	ReplicationKind kind;
 	char	   *plugin;
+	bool		reserve_wal;
 } CreateReplicationSlotCmd;