diff --git a/Zend/zend_smart_str.c b/Zend/zend_smart_str.c
index e6002dcf1d5..5132043c60e 100644
--- a/Zend/zend_smart_str.c
+++ b/Zend/zend_smart_str.c
@@ -181,7 +181,7 @@ ZEND_API void ZEND_FASTCALL _smart_string_alloc(smart_string *str, size_t len)
 	}
 }
 
-ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, zend_string *value, size_t length)
+ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, const zend_string *value, size_t length)
 {
 	smart_str_append_escaped(str, ZSTR_VAL(value), MIN(length, ZSTR_LEN(value)));
 
@@ -190,7 +190,7 @@ ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, z
 	}
 }
 
-ZEND_API void ZEND_FASTCALL smart_str_append_scalar(smart_str *dest, zval *value, size_t truncate) {
+ZEND_API void ZEND_FASTCALL smart_str_append_scalar(smart_str *dest, const zval *value, size_t truncate) {
 	ZEND_ASSERT(Z_TYPE_P(value) <= IS_STRING);
 
 	switch (Z_TYPE_P(value)) {
diff --git a/Zend/zend_smart_str.h b/Zend/zend_smart_str.h
index d8b72905d02..e271835e41d 100644
--- a/Zend/zend_smart_str.h
+++ b/Zend/zend_smart_str.h
@@ -32,8 +32,8 @@ ZEND_API void ZEND_FASTCALL smart_str_append_double(
 		smart_str *str, double num, int precision, bool zero_fraction);
 ZEND_API void smart_str_append_printf(smart_str *dest, const char *format, ...)
 	ZEND_ATTRIBUTE_FORMAT(printf, 2, 3);
-ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, zend_string *value, size_t length);
-ZEND_API void ZEND_FASTCALL smart_str_append_scalar(smart_str *str, zval *value, size_t truncate);
+ZEND_API void ZEND_FASTCALL smart_str_append_escaped_truncated(smart_str *str, const zend_string *value, size_t length);
+ZEND_API void ZEND_FASTCALL smart_str_append_scalar(smart_str *str, const zval *value, size_t truncate);
 END_EXTERN_C()
 
 static zend_always_inline size_t smart_str_alloc(smart_str *str, size_t len, bool persistent) {