diff --git a/contrib/chkpass/chkpass--1.0.sql b/contrib/chkpass/chkpass--1.0.sql
index d1fbedc4468..406a61924cc 100644
--- a/contrib/chkpass/chkpass--1.0.sql
+++ b/contrib/chkpass/chkpass--1.0.sql
@@ -10,12 +10,15 @@
 CREATE FUNCTION chkpass_in(cstring)
 	RETURNS chkpass
 	AS 'MODULE_PATHNAME'
-	LANGUAGE C STRICT;
+	LANGUAGE C STRICT VOLATILE;
+-- Note: chkpass_in actually is volatile, because of its use of random().
+-- In hindsight that was a bad idea, but there's no way to change it without
+-- breaking some usage patterns.
 
 CREATE FUNCTION chkpass_out(chkpass)
 	RETURNS cstring
 	AS 'MODULE_PATHNAME'
-	LANGUAGE C STRICT;
+	LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE chkpass (
 	internallength = 16,
diff --git a/contrib/ltree/ltree--1.0.sql b/contrib/ltree/ltree--1.0.sql
index 5a2f375a4f3..7d55fc603f6 100644
--- a/contrib/ltree/ltree--1.0.sql
+++ b/contrib/ltree/ltree--1.0.sql
@@ -6,12 +6,12 @@
 CREATE FUNCTION ltree_in(cstring)
 RETURNS ltree
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE FUNCTION ltree_out(ltree)
 RETURNS cstring
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE ltree (
 	INTERNALLENGTH = -1,
@@ -303,12 +303,12 @@ CREATE OPERATOR CLASS ltree_ops
 CREATE FUNCTION lquery_in(cstring)
 RETURNS lquery
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE FUNCTION lquery_out(lquery)
 RETURNS cstring
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE lquery (
 	INTERNALLENGTH = -1,
@@ -414,12 +414,12 @@ CREATE OPERATOR ^? (
 CREATE FUNCTION ltxtq_in(cstring)
 RETURNS ltxtquery
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE FUNCTION ltxtq_out(ltxtquery)
 RETURNS cstring
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE ltxtquery (
 	INTERNALLENGTH = -1,
@@ -481,12 +481,12 @@ CREATE OPERATOR ^@ (
 CREATE FUNCTION ltree_gist_in(cstring)
 RETURNS ltree_gist
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE FUNCTION ltree_gist_out(ltree_gist)
 RETURNS cstring
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE ltree_gist (
 	internallength = -1,
diff --git a/contrib/pg_trgm/pg_trgm--1.1.sql b/contrib/pg_trgm/pg_trgm--1.1.sql
index 1fff7af2c48..34b37e47872 100644
--- a/contrib/pg_trgm/pg_trgm--1.1.sql
+++ b/contrib/pg_trgm/pg_trgm--1.1.sql
@@ -53,12 +53,12 @@ CREATE OPERATOR <-> (
 CREATE FUNCTION gtrgm_in(cstring)
 RETURNS gtrgm
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE FUNCTION gtrgm_out(gtrgm)
 RETURNS cstring
 AS 'MODULE_PATHNAME'
-LANGUAGE C STRICT;
+LANGUAGE C STRICT IMMUTABLE;
 
 CREATE TYPE gtrgm (
         INTERNALLENGTH = -1,