diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index ea9740e3f8..80b8654fc8 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -532,21 +532,22 @@ plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo,
 									  false);
 
 					/*
-					 * Force any array-valued parameter to be stored in
-					 * expanded form in our local variable, in hopes of
-					 * improving efficiency of uses of the variable.  (This is
-					 * a hack, really: why only arrays? Need more thought
-					 * about which cases are likely to win.  See also
-					 * typisarray-specific heuristic in exec_assign_value.)
-					 *
-					 * Special cases: If passed a R/W expanded pointer, assume
+					 * If it's a pass-by-reference type, check to see if we
+					 * received a R/W expanded-object pointer.  If so, assume
 					 * we can commandeer the object rather than having to copy
 					 * it.  If passed a R/O expanded pointer, just keep it as
 					 * the value of the variable for the moment.  (We'll force
 					 * it to R/W if the variable gets modified, but that may
 					 * very well never happen.)
+					 *
+					 * Also, force any flat array value to be stored in
+					 * expanded form in our local variable, in hopes of
+					 * improving efficiency of uses of the variable.  (This is
+					 * a hack, really: why only arrays? Need more thought
+					 * about which cases are likely to win.  See also
+					 * typisarray-specific heuristic in exec_assign_value.)
 					 */
-					if (!var->isnull && var->datatype->typisarray)
+					if (!var->isnull && var->datatype->typlen == -1)
 					{
 						if (VARATT_IS_EXTERNAL_EXPANDED_RW(DatumGetPointer(var->value)))
 						{
@@ -561,7 +562,7 @@ plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo,
 						{
 							/* R/O pointer, keep it as-is until assigned to */
 						}
-						else
+						else if (var->datatype->typisarray)
 						{
 							/* flat array, so force to expanded form */
 							assign_simple_var(&estate, var,