diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 3e7b6891f2e..7fa2d5e1d4b 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4243,7 +4243,9 @@ getFuncs(Archive *fout, int *numFuncs)
 	 * 3. Otherwise, we normally exclude functions in pg_catalog.  However, if
 	 * they're members of extensions and we are in binary-upgrade mode then
 	 * include them, since we want to dump extension members individually in
-	 * that mode.
+	 * that mode.  Also, if they are used by casts then we need to gather the
+	 * information about them, though they won't be dumped if they are
+	 * built-in.
 	 */
 
 	if (fout->remoteVersion >= 70300)
@@ -4261,11 +4263,15 @@ getFuncs(Archive *fout, int *numFuncs)
 							   "\n  AND NOT EXISTS (SELECT 1 FROM pg_depend "
 								 "WHERE classid = 'pg_proc'::regclass AND "
 								 "objid = p.oid AND deptype = 'i')");
-		appendPQExpBufferStr(query,
+		appendPQExpBuffer(query,
 							 "\n  AND ("
 							 "\n  pronamespace != "
 							 "(SELECT oid FROM pg_namespace "
-							 "WHERE nspname = 'pg_catalog')");
+							 "WHERE nspname = 'pg_catalog')"
+							 "\n  OR EXISTS (SELECT 1 FROM pg_cast"
+							 "\n  WHERE pg_cast.oid > '%u'::oid"
+							 "\n  AND p.oid = pg_cast.castfunc)",
+							 g_last_builtin_oid);
 		if (binary_upgrade && fout->remoteVersion >= 90100)
 			appendPQExpBufferStr(query,
 							   "\n  OR EXISTS(SELECT 1 FROM pg_depend WHERE "
@@ -10296,7 +10302,8 @@ dumpCast(Archive *fout, CastInfo *cast)
 	{
 		funcInfo = findFuncByOid(cast->castfunc);
 		if (funcInfo == NULL)
-			return;
+			exit_horribly(NULL, "unable to find function definition for OID %u",
+						  cast->castfunc);
 	}
 
 	/*