diff --git a/src/util/conv.c b/src/util/conv.c
index 5f1563b54..e4e7a08b4 100644
--- a/src/util/conv.c
+++ b/src/util/conv.c
@@ -356,7 +356,7 @@ add_quoted_to_string(struct string *string, const char *src, int len)
 }
 
 struct string *
-add_shell_quoted_to_string(struct string *string, char *src, int len)
+add_shell_quoted_to_string(struct string *string, const char *src, int len)
 {
 	add_char_to_string(string, '\'');
 	for (; len; len--, ++src)
@@ -370,7 +370,7 @@ add_shell_quoted_to_string(struct string *string, char *src, int len)
 }
 
 struct string *
-add_shell_safe_to_string(struct string *string, char *cmd, int cmdlen)
+add_shell_safe_to_string(struct string *string, const char *cmd, int cmdlen)
 {
 	int prev_safe = 0;
 
diff --git a/src/util/conv.h b/src/util/conv.h
index a953df741..dd7555714 100644
--- a/src/util/conv.h
+++ b/src/util/conv.h
@@ -112,11 +112,11 @@ struct string *add_quoted_to_string(struct string *string, const char *q, int ql
  * and ' to @a string.
  * @relates string */
 struct string *add_shell_quoted_to_string(struct string *string,
-					  char *src, int len);
+					  const char *src, int len);
 
 /* Escapes non shell safe chars with '_'.
  * @relates string */
-struct string *add_shell_safe_to_string(struct string *string, char *cmd, int cmdlen);
+struct string *add_shell_safe_to_string(struct string *string, const char *cmd, int cmdlen);
 
 /** @} */