diff --git a/ChangeLog b/ChangeLog
index 582fec1707..1d7e032b1a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Apr 11 03:33:05 2013  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/fiddle/closure.c (initialize): check mprotect's return value.
+	  If mprotect is failed because of PaX or something, its function call
+	  will cause SEGV.
+	  http://c5664.rubyci.org/~chkbuild/ruby-trunk/log/20130401T210301Z.diff.html.gz
+
 Wed Apr 10 17:39:13 2013  Tanaka Akira  <akr@fsij.org>
 
 	* ext/bigdecimal/bigdecimal.c (VpCtoV): Initialize a local variable
diff --git a/ext/fiddle/closure.c b/ext/fiddle/closure.c
index fdb2233b22..d064f11991 100644
--- a/ext/fiddle/closure.c
+++ b/ext/fiddle/closure.c
@@ -228,7 +228,10 @@ initialize(int rbargc, VALUE argv[], VALUE self)
 #else
     result = ffi_prep_closure(pcl, cif, callback, (void *)self);
     cl->code = (void *)pcl;
-    mprotect(pcl, sizeof(pcl), PROT_READ | PROT_EXEC);
+    i = mprotect(pcl, sizeof(pcl), PROT_READ | PROT_EXEC);
+    if (i) {
+	rb_sys_fail("mprotect");
+    }
 #endif
 
     if (FFI_OK != result)