diff --git a/contrib/unaccent/unaccent.sql.in b/contrib/unaccent/unaccent.sql.in
index 7e397cc8d2..6d712e7bb8 100644
--- a/contrib/unaccent/unaccent.sql.in
+++ b/contrib/unaccent/unaccent.sql.in
@@ -6,12 +6,12 @@ SET search_path = public;
 CREATE OR REPLACE FUNCTION unaccent(regdictionary, text)
 	RETURNS text
 	AS 'MODULE_PATHNAME', 'unaccent_dict'
-	LANGUAGE C STRICT;
+	LANGUAGE C STABLE STRICT;
 
 CREATE OR REPLACE FUNCTION unaccent(text)
 	RETURNS text
 	AS 'MODULE_PATHNAME', 'unaccent_dict'
-	LANGUAGE C STRICT;
+	LANGUAGE C STABLE STRICT;
 
 CREATE OR REPLACE FUNCTION unaccent_init(internal)
 	RETURNS internal