1 files changed, 1 insertions, 1 deletions

diff --git a/ruby.h b/ruby.h
index f51a81292e..4281ad4a0e 100644
--- a/ruby.h
+++ b/ruby.h
@@ -166,7 +166,7 @@ VALUE rb_ull2inum _((unsigned LONG_LONG));
 #define FIX2LONG(x) RSHIFT((long)x,1)
 #define FIX2ULONG(x) (((unsigned long)(x))>>1)
 #define FIXNUM_P(f) (((long)(f))&FIXNUM_FLAG)
-#define POSFIXABLE(f) ((f) <= FIXNUM_MAX)
+#define POSFIXABLE(f) ((f) < FIXNUM_MAX+1)
 #define NEGFIXABLE(f) ((f) >= FIXNUM_MIN)
 #define FIXABLE(f) (POSFIXABLE(f) && NEGFIXABLE(f))