diff --git a/.gitignore b/.gitignore
index e236684..2514b52 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+/.build/
 /.bundle/
 /.yardoc
 /Gemfile.lock
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 24f3cc1..a689e6e 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -34,6 +34,7 @@ STRINGIO_VERSION = "3.2.1";
 # define NUM2ULEN(num) NUM2ULONG(num)
 # define LEN2NUM(num) LONG2NUM(num)
 # define ULEN2NUM(num) ULONG2NUM(num)
+# define PRIdLEN "ld"
 typedef long rb_len_t;
 typedef unsigned long rb_ulen_t;
 #endif
@@ -959,15 +960,14 @@ strio_seek(int argc, VALUE *argv, VALUE self)
     if (CLOSED(self)) {
 	rb_raise(rb_eIOError, "closed stream");
     }
-    switch (whence) {
-      case Qnil:
-      case INT2FIX(0):
+    switch (NIL_P(whence) ? 0 : NUM2LONG(whence)) {
+      case 0:
 	offset = 0;
 	break;
-      case INT2FIX(1):
+      case 1:
 	offset = ptr->pos;
 	break;
-      case INT2FIX(2):
+      case 2:
 	if (NIL_P(ptr->string)) {
 	    offset = 0;
 	}
@@ -1734,7 +1734,7 @@ strio_read(int argc, VALUE *argv, VALUE self)
 	if (!NIL_P(argv[0])) {
 	    len = NUM2LEN(argv[0]);
 	    if (len < 0) {
-		rb_raise(rb_eArgError, "negative length %ld given", len);
+		rb_raise(rb_eArgError, "negative length %"PRIdLEN" given", len);
 	    }
 	    if (eos_p(ptr)) {
 		if (!NIL_P(str)) rb_str_resize(str, 0);
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index 413f5a4..fd88de5 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -513,6 +513,8 @@ def test_seek
     assert_raise(Errno::EINVAL) { f.seek(-1) }
     f.seek(-1, 2)
     assert_equal("4", f.getc)
+    f.seek(-2, 2.0)
+    assert_equal("3", f.getc)
     assert_raise(Errno::EINVAL) { f.seek(1, 3) }
     f.close
     assert_raise(IOError) { f.seek(0) }