diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index b051707..04013b6 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -554,6 +554,24 @@ func_match_argtypes(int nargs,
 		}
 	}
 
+	if (ncandidates == 0)
+	{
+		/* try again with assignment rules */
+		for (current_candidate = raw_candidates;
+			 current_candidate != NULL;
+			 current_candidate = next_candidate)
+		{
+			next_candidate = current_candidate->next;
+			if (can_coerce_type(nargs, input_typeids, current_candidate->args,
+								COERCION_ASSIGNMENT))
+			{
+				current_candidate->next = *candidates;
+				*candidates = current_candidate;
+				ncandidates++;
+			}
+		}
+	}
+
 	return ncandidates;
 }	/* func_match_argtypes() */
 
@@ -1354,7 +1372,7 @@ make_fn_arguments(ParseState *pstate,
 								   (Node *) na->arg,
 								   actual_arg_types[i],
 								   declared_arg_types[i], -1,
-								   COERCION_IMPLICIT,
+								   COERCION_ASSIGNMENT,
 								   COERCE_IMPLICIT_CAST,
 								   -1);
 				na->arg = (Expr *) node;
@@ -1365,7 +1383,7 @@ make_fn_arguments(ParseState *pstate,
 								   node,
 								   actual_arg_types[i],
 								   declared_arg_types[i], -1,
-								   COERCION_IMPLICIT,
+								   COERCION_ASSIGNMENT,
 								   COERCE_IMPLICIT_CAST,
 								   -1);
 				lfirst(current_fargs) = node;