diff --git a/ChangeLog b/ChangeLog
index 9d73e817f4..560a00ea72 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Sep 18 19:43:04 2008  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* st.c (new_size): raise RuntimeError when st_table is too big.
+
 Thu Sep 18 18:23:23 2008  Tanaka Akira  <akr@fsij.org>
 
 	* transcode.c (enc_arg): must take pointer argument to avoid GC
diff --git a/st.c b/st.c
index a51d7cf8c8..54e10721b0 100644
--- a/st.c
+++ b/st.c
@@ -6,9 +6,7 @@
 #include "regint.h"
 #include "st.h"
 #else
-#include "ruby/config.h"
-#include "ruby/defines.h"
-#include "ruby/st.h"
+#include "ruby/ruby.h"
 #endif
 
 #include <stdio.h>
@@ -135,6 +133,9 @@ new_size(int size)
 	if (newsize > size) return primes[i];
     }
     /* Ran out of polynomials */
+#ifndef NOT_RUBY
+    rb_raise(rb_eRuntimeError, "st_table too big");
+#endif
     return -1;			/* should raise exception */
 #endif
 }