diff --git a/ext/filter/filter.c b/ext/filter/filter.c
index 379284e8fb9..4de7791c67f 100644
--- a/ext/filter/filter.c
+++ b/ext/filter/filter.c
@@ -382,7 +382,7 @@ static unsigned int php_sapi_filter(int arg, char *var, char **val, unsigned int
 		}
 		efree(*val);
 		if (Z_STRLEN(new_var)) {
-			*val = estrdup(Z_STRVAL(new_var));
+			*val = estrndup(Z_STRVAL(new_var), Z_STRLEN(new_var) + 1);
 			zval_dtor(&new_var);
 		} else {
 			*val = estrdup("");