diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index de84b77..e8a9fee 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4671,6 +4671,11 @@ local0.*    /var/log/postgresql
             </thead>
            <tbody>
             <row>
+             <entry><literal>%C</literal></entry>
+             <entry>Cluster name</entry>
+             <entry>no</entry>
+            </row>
+            <row>
              <entry><literal>%a</literal></entry>
              <entry>Application name</entry>
              <entry>yes</entry>
@@ -5075,6 +5080,10 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         The process title is typically viewed using programs like
         <application>ps</> or, on Windows, <application>Process Explorer</>.
        </para>
+       <para>
+        The cluster name can also be included in log files.  See 
+        <varname>log_line_prefix</varname> for details.
+       </para>
       </listitem>
      </varlistentry>
 
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 9005b26..9fe40f8 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2413,6 +2413,12 @@ log_line_prefix(StringInfo buf, ErrorData *edata)
 				else
 					appendStringInfo(buf, "%lx.%x", (long) (MyStartTime), MyProcPid);
 				break;
+			case 'C':
+				if (padding != 0)
+					appendStringInfo(buf, "%*s", padding, cluster_name);
+				else
+					appendStringInfoString(buf, cluster_name);
+				break;
 			case 'p':
 				if (padding != 0)
 					appendStringInfo(buf, "%*d", padding, MyProcPid);
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 09b2003..748e6cc 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -421,6 +421,7 @@
 #log_error_verbosity = default		# terse, default, or verbose messages
 #log_hostname = off
 #log_line_prefix = ''			# special values:
+					#   %C = cluster name
 					#   %a = application name
 					#   %u = user name
 					#   %d = database name