diff --git a/ChangeLog b/ChangeLog
index 84cd2a45fc..2ade3a2ca5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jul 12 22:41:39 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* include/ruby/ruby.h (PRI_PTRDIFF_PREFIX, PRI_SIZE_PREFIX): fixed typo.
+
 Sat Jul 12 22:30:43 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/intern.h (HAVE_RUBY_RUBY_H): defines macros so that
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 67c22af9ad..b297231ea4 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -106,11 +106,11 @@ typedef unsigned LONG_LONG ID;
 #define PRIXVALUE PRI_VALUE_PREFIX"X"
 
 #if SIZEOF_PTRDIFF_T == SIZEOF_INT
-# define PRI_PTDIFF_PREFIX
+# define PRI_PTRDIFF_PREFIX
 #elif SIZEOF_PTRDIFF_T == SIZEOF_LONG
-# define PRI_PTDIFF_PREFIX "l"
+# define PRI_PTRDIFF_PREFIX "l"
 #elif SIZEOF_PTRDIFF_T == SIZEOF_LONG
-# define PRI_PTDIFF_PREFIX "ll"
+# define PRI_PTRDIFF_PREFIX "ll"
 #endif
 #define PRIdPTRDIFF PRI_PTRDIFF_PREFIX"d"
 #define PRIiPTRDIFF PRI_PTRDIFF_PREFIX"i"
@@ -120,11 +120,11 @@ typedef unsigned LONG_LONG ID;
 #define PRIXPTRDIFF PRI_PTRDIFF_PREFIX"X"
 
 #if SIZEOF_SIZE_T == SIZEOF_INT
-# define PRI_PTDIFF_PREFIX
+# define PRI_SIZE_PREFIX
 #elif SIZEOF_SIZE_T == SIZEOF_LONG
-# define PRI_PTDIFF_PREFIX "l"
+# define PRI_SIZE_PREFIX "l"
 #elif SIZEOF_SIZE_T == SIZEOF_LONG
-# define PRI_PTDIFF_PREFIX "ll"
+# define PRI_SIZE_PREFIX "ll"
 #endif
 #define PRIdSIZE PRI_SIZE_PREFIX"d"
 #define PRIiSIZE PRI_SIZE_PREFIX"i"