1 files changed, 1 insertions, 1 deletions

diff --git a/src/sp_utils.c b/src/sp_utils.c
index 41d817e..e872abd 100644
--- a/src/sp_utils.c
+++ b/src/sp_utils.c
@@ -151,7 +151,7 @@ static char* zend_string_to_char(const zend_string* zs) {
   return copy;
 }
 
-const zend_string* sp_zval_to_zend_string(zval* zv) {
+const zend_string* sp_zval_to_zend_string(const zval* zv) {
   switch (Z_TYPE_P(zv)) {
     case IS_LONG: {
       char* msg;