diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index dc6528dc11..7b8ae9fac3 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -1650,7 +1650,10 @@ INSERT INTO tbl1 VALUES ($1, $2) \bind 'first value' 'second value' \g
         If the form <literal>\df+</literal> is used, additional information
         about each function is shown, including volatility,
         parallel safety, owner, security classification, access privileges,
-        language, source code and description.
+        language, internal name (for C and internal functions only),
+        and description.
+        Source code for a specific function can be seen
+        using <literal>\sf</literal>.
         </para>
 
         </listitem>
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index c8a0bb7b3a..2084f5ccda 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -410,14 +410,9 @@ describeFunctions(const char *functypes, const char *func_pattern,
 		appendPQExpBuffer(&buf,
 						  ",\n l.lanname as \"%s\"",
 						  gettext_noop("Language"));
-		if (pset.sversion >= 140000)
-			appendPQExpBuffer(&buf,
-							  ",\n COALESCE(pg_catalog.pg_get_function_sqlbody(p.oid), p.prosrc) as \"%s\"",
-							  gettext_noop("Source code"));
-		else
-			appendPQExpBuffer(&buf,
-							  ",\n p.prosrc as \"%s\"",
-							  gettext_noop("Source code"));
+		appendPQExpBuffer(&buf,
+						  ",\n CASE WHEN l.lanname IN ('internal', 'c') THEN p.prosrc END as \"%s\"",
+						  gettext_noop("Internal name"));
 		appendPQExpBuffer(&buf,
 						  ",\n pg_catalog.obj_description(p.oid, 'pg_proc') as \"%s\"",
 						  gettext_noop("Description"));
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index 8fc62cebd2..0f349df344 100644
--- a/src/test/regress/expected/psql.out
+++ b/src/test/regress/expected/psql.out
@@ -5247,6 +5247,34 @@ reset work_mem;
  pg_catalog | &&   | anyarray      | anyarray       | boolean     | overlaps
 (1 row)
 
+-- check \df+
+begin;
+-- we have to use functions with a predictable owner name, so make a role
+create role regress_psql_user superuser;
+set session authorization regress_psql_user;
+create function psql_df_internal (float8)
+  returns float8
+  language internal immutable parallel safe strict
+  as 'dsin';
+create function psql_df_sql (x integer)
+  returns integer
+  security definer
+  begin atomic select x + 1; end;
+create function psql_df_plpgsql ()
+  returns void
+  language plpgsql
+  as $$ begin return; end; $$;
+comment on function psql_df_plpgsql () is 'some comment';
+\df+ psql_df_*
+                                                                                       List of functions
+ Schema |       Name       | Result data type | Argument data types | Type | Volatility | Parallel |       Owner       | Security | Access privileges | Language | Internal name | Description  
+--------+------------------+------------------+---------------------+------+------------+----------+-------------------+----------+-------------------+----------+---------------+--------------
+ public | psql_df_internal | double precision | double precision    | func | immutable  | safe     | regress_psql_user | invoker  |                   | internal | dsin          | 
+ public | psql_df_plpgsql  | void             |                     | func | volatile   | unsafe   | regress_psql_user | invoker  |                   | plpgsql  |               | some comment
+ public | psql_df_sql      | integer          | x integer           | func | volatile   | unsafe   | regress_psql_user | definer  |                   | sql      |               | 
+(3 rows)
+
+rollback;
 -- check \sf
 \sf information_schema._pg_expandarray
 CREATE OR REPLACE FUNCTION information_schema._pg_expandarray(anyarray, OUT x anyelement, OUT n integer)
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 2da9665a19..e4ed6cda1f 100644
--- a/src/test/regress/sql/psql.sql
+++ b/src/test/regress/sql/psql.sql
@@ -1275,6 +1275,29 @@ reset work_mem;
 \do - pg_catalog.int4
 \do && anyarray *
 
+-- check \df+
+begin;
+-- we have to use functions with a predictable owner name, so make a role
+create role regress_psql_user superuser;
+set session authorization regress_psql_user;
+
+create function psql_df_internal (float8)
+  returns float8
+  language internal immutable parallel safe strict
+  as 'dsin';
+create function psql_df_sql (x integer)
+  returns integer
+  security definer
+  begin atomic select x + 1; end;
+create function psql_df_plpgsql ()
+  returns void
+  language plpgsql
+  as $$ begin return; end; $$;
+comment on function psql_df_plpgsql () is 'some comment';
+
+\df+ psql_df_*
+rollback;
+
 -- check \sf
 \sf information_schema._pg_expandarray
 \sf+ information_schema._pg_expandarray