diff --git a/main.h b/main.h
index ed076e9..4955293 100644
--- a/main.h
+++ b/main.h
@@ -1,7 +1,7 @@
 #ifndef MAIN_H_
 #define MAIN_H_
 int _printf(const char *format, ...);
-int _contains(char *str, char c);
+int _contains(const char *str, char c);
 int _strlen(char *str);
 
 
diff --git a/strings.c b/strings.c
index 00365f2..253796d 100644
--- a/strings.c
+++ b/strings.c
@@ -9,7 +9,7 @@
  */
 int _strlen(char *str)
 {
-  if (*str)
+  if (str)
     return (1 + _strlen(str++));
   else
     return (0);
@@ -23,7 +23,7 @@ int _strlen(char *str)
  *
  * Return: number of unique cases of "%*" that aren't "%%"
  */
-int _contains(char *str, char c)
+int _contains(const char *str, char c)
 {
   if (*str)
   {