diff --git a/src/h/external.h b/src/h/external.h
index 375b66db7..46cd877fe 100755
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -1686,7 +1686,6 @@ extern ECL_API cl_object cl_get_universal_time(void);
 
 extern ECL_API void assert_type_integer(cl_object p);
 extern ECL_API void assert_type_non_negative_integer(cl_object p);
-extern ECL_API void assert_type_string(cl_object p);
 extern ECL_API void assert_type_readtable(cl_object p);
 extern ECL_API void assert_type_hash_table(cl_object p);
 extern ECL_API void assert_type_proper_list(cl_object p);