diff --git a/src/sp_utils.c b/src/sp_utils.c
index 6b40e99..faf2e9a 100644
--- a/src/sp_utils.c
+++ b/src/sp_utils.c
@@ -30,7 +30,7 @@ void sp_log_msg(char const *feature, char const *level, const char* fmt, ...) {
 }
 
 
-zend_always_inline char* sp_getenv(const char* var) {
+zend_always_inline char* sp_getenv(char* var) {
   if (sapi_module.getenv) {
     return sapi_module.getenv(ZEND_STRL(var));
   } else {
diff --git a/src/sp_utils.h b/src/sp_utils.h
index 5b22e8a..61a4c53 100644
--- a/src/sp_utils.h
+++ b/src/sp_utils.h
@@ -58,7 +58,7 @@ void sp_log_disable(const char *restrict, const char *restrict,
                     const char *restrict, const sp_disabled_function *);
 void sp_log_disable_ret(const char *restrict, const char *restrict,
                         const sp_disabled_function *);
-char *sp_getenv(const char *);
+char *sp_getenv(char *);
 int is_regexp_matching(const pcre *, const char *);
 int hook_function(const char *, HashTable *,
                   void (*)(INTERNAL_FUNCTION_PARAMETERS), bool);