diff --git a/hash.c b/hash.c
index d6ac93fbc7..56cedf072b 100644
--- a/hash.c
+++ b/hash.c
@@ -2547,14 +2547,16 @@ env_str_new2(const char *ptr)
      rb_raise(rb_eArgError, "bad environment variable " #var) : (void)0)
 
 static inline const char *
-env_name(VALUE s)
+env_name(volatile VALUE *s)
 {
     const char *name;
-    SafeStringValue(s);
-    get_env_ptr(name, s);
+    SafeStringValue(*s);
+    get_env_ptr(name, *s);
     return name;
 }
 
+#define env_name(s) env_name(&(s))
+
 static VALUE
 env_delete(VALUE obj, VALUE name)
 {