diff --git a/ChangeLog b/ChangeLog
index fdaf4d2042..a4f154ea58 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Dec 13 18:35:11 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/fiddle/conversions.h (PTR2NUM): use signed integer to make
+	  Fixnum for negative values.
+
 Sun Dec 13 18:33:41 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* pack.c (pack_pack): always check index range against the
diff --git a/ext/fiddle/conversions.h b/ext/fiddle/conversions.h
index d0a08d6bc0..cbc610bad2 100644
--- a/ext/fiddle/conversions.h
+++ b/ext/fiddle/conversions.h
@@ -33,11 +33,11 @@ VALUE generic_to_value(VALUE rettype, fiddle_generic retval);
 #define GENERIC2VALUE(_type, _retval) generic_to_value((_type), (_retval))
 
 #if SIZEOF_VOIDP == SIZEOF_LONG
-# define PTR2NUM(x)   (ULONG2NUM((unsigned long)(x)))
+# define PTR2NUM(x)   (LONG2NUM((long)(x)))
 # define NUM2PTR(x)   ((void*)(NUM2ULONG(x)))
 #else
 /* # error --->> Ruby/DL2 requires sizeof(void*) == sizeof(long) to be compiled. <<--- */
-# define PTR2NUM(x)   (ULL2NUM((unsigned long long)(x)))
+# define PTR2NUM(x)   (LL2NUM((LONG_LONG)(x)))
 # define NUM2PTR(x)   ((void*)(NUM2ULL(x)))
 #endif