diff --git a/src/pl/plpgsql/src/pl_comp.c b/src/pl/plpgsql/src/pl_comp.c
index e9d7ef5..f450156 100644
--- a/src/pl/plpgsql/src/pl_comp.c
+++ b/src/pl/plpgsql/src/pl_comp.c
@@ -433,9 +433,14 @@ do_compile(FunctionCallInfo fcinfo,
 							 errmsg("PL/pgSQL functions cannot accept type %s",
 									format_type_be(argtypeid))));
 
-				/* Build variable and add to datum list */
-				argvariable = plpgsql_build_variable(buf, 0,
-													 argdtype, false);
+				/*
+				 * Build variable and add to datum list.  If there's a name for
+				 * the argument, then use that else use $n name.
+				 */
+				argvariable = plpgsql_build_variable((argnames != NULL &&
+													  argnames[i][0] != '\0') ?
+													 argnames[i] : buf,
+													 0, argdtype, false);
 
 				if (argvariable->dtype == PLPGSQL_DTYPE_VAR)
 				{
@@ -461,7 +466,7 @@ do_compile(FunctionCallInfo fcinfo,
 				add_parameter_name(argitemtype, argvariable->dno, buf);
 
 				/* If there's a name for the argument, make an alias */
-				if (argnames && argnames[i][0] != '\0')
+				if (argnames != NULL && argnames[i][0] != '\0')
 					add_parameter_name(argitemtype, argvariable->dno,
 									   argnames[i]);
 			}
diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index 7109996..cf589d5 100644
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -6029,3 +6029,17 @@ SELECT * FROM list_partitioned_table() AS t;
  2
 (2 rows)
 
+--
+-- Check argument name is used instead of $n
+--
+CREATE TYPE ct AS (a int, b int);
+-- Should fail, error message should contain argument name instead of $1
+CREATE OR REPLACE FUNCTION fx(x ct) RETURNS void AS $$
+BEGIN
+  GET DIAGNOSTICS x = ROW_COUNT;
+  RETURN;
+END; $$ LANGUAGE plpgsql;
+ERROR:  "x" is not a scalar variable
+LINE 3:   GET DIAGNOSTICS x = ROW_COUNT;
+                          ^
+DROP TYPE ct;
diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index 771d682..42f51e9 100644
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -4811,3 +4811,17 @@ BEGIN
 END; $$ LANGUAGE plpgsql;
 
 SELECT * FROM list_partitioned_table() AS t;
+
+--
+-- Check argument name is used instead of $n
+--
+CREATE TYPE ct AS (a int, b int);
+
+-- Should fail, error message should contain argument name instead of $1
+CREATE OR REPLACE FUNCTION fx(x ct) RETURNS void AS $$
+BEGIN
+  GET DIAGNOSTICS x = ROW_COUNT;
+  RETURN;
+END; $$ LANGUAGE plpgsql;
+
+DROP TYPE ct;