diff --git a/ctype/ctype.c b/ctype/ctype.c
index e86c5b03c7..6cb8000771 100644
--- a/ctype/ctype.c
+++ b/ctype/ctype.c
@@ -45,9 +45,11 @@ tolower (int c)
 {
   return c >= -128 && c < 256 ? __ctype_tolower[c] : c;
 }
+libc_hidden_def (tolower)
 
 int
 toupper (int c)
 {
   return c >= -128 && c < 256 ? __ctype_toupper[c] : c;
 }
+libc_hidden_def (toupper)
diff --git a/include/ctype.h b/include/ctype.h
index ac6db790b7..493a6f80ce 100644
--- a/include/ctype.h
+++ b/include/ctype.h
@@ -11,6 +11,9 @@ libc_hidden_proto (__ctype_init)
    So defeat macro expansion with parens for this declaration.  */
 extern int (__isctype) (int __c, int __mask);
 
+libc_hidden_proto (tolower)
+libc_hidden_proto (toupper)
+
 # if IS_IN (libc)
 
 /* These accessors are used by the optimized macros to find the