diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 2f1ef6cb1b4..466a3739857 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4204,7 +4204,9 @@ 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)
@@ -4226,7 +4228,11 @@ getFuncs(Archive *fout, int *numFuncs)
 						  "\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)
 			appendPQExpBuffer(query,
 							  "\n  OR EXISTS(SELECT 1 FROM pg_depend WHERE "
@@ -10170,7 +10176,8 @@ 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);
 	}
 
 	/*