diff --git a/include/libssh/libssh.h b/include/libssh/libssh.h
index eb2b466b..ef383015 100644
--- a/include/libssh/libssh.h
+++ b/include/libssh/libssh.h
@@ -185,7 +185,7 @@ const char *ssh_copyright(void);
 /* makestring returns a newly allocated string from a char * ptr */
 STRING *string_from_char(const char *what);
 /* it returns the string len in host byte orders. str->size is big endian warning ! */
-int string_len(STRING *str);
+u32 string_len(STRING *str);
 STRING *string_new(unsigned int size);
 /* string_fill copies the data in the string. it does NOT check for boundary so allocate enough place with string_new */
 void string_fill(STRING *str, const void *data,int len);
diff --git a/libssh/string.c b/libssh/string.c
index 45bd02cf..17f9cb85 100644
--- a/libssh/string.c
+++ b/libssh/string.c
@@ -63,7 +63,7 @@ STRING *string_from_char(const char *what){
  * \param str the input SSH string
  * \return size of the content of str
  */
-int string_len(STRING *str){
+u32 string_len(STRING *str){
 	return ntohl(str->size);
 }