diff --git a/ChangeLog b/ChangeLog
index 39222b7978..42f880dd2e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu May 24 12:07:27 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* cont.c: check across trap violation.
+
+	* eval.c, yarvcore.h: ditto.
+
 Thu May 24 11:46:55 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* gc.c, yarvcore.c: fix to mark VM structure on startup.
diff --git a/cont.c b/cont.c
index 099cdde070..928f9381ad 100644
--- a/cont.c
+++ b/cont.c
@@ -270,8 +270,9 @@ rb_cont_call(int argc, VALUE *argv, VALUE contval)
     if (cont->saved_thread.value != th->value) {
 	rb_raise(rb_eRuntimeError, "continuation called across threads");
     }
-    /* TODO: check "continuation called across trap" */
-    printf("--> %p\n", cont);
+    if (cont->saved_thread.trap_tag != th->trap_tag) {
+	rb_raise(rb_eRuntimeError, "continuation called across trap");
+    }
 
     switch(argc) {
       case 0:
diff --git a/eval.c b/eval.c
index d0f85ccad2..571b84a57d 100644
--- a/eval.c
+++ b/eval.c
@@ -1162,11 +1162,16 @@ rb_protect(VALUE (*proc) (VALUE), VALUE data, int *state)
     int status;
     rb_thread_t *th = GET_THREAD();
     rb_control_frame_t *cfp = th->cfp;
+    struct rb_vm_trap_tag trap_tag = {
+	th->trap_tag,
+    };
 
     PUSH_TAG();
+    th->trap_tag = &trap_tag;
     if ((status = EXEC_TAG()) == 0) {
 	result = (*proc) (data);
     }
+    th->trap_tag = trap_tag.prev;
     POP_TAG();
 
     if (state) {
diff --git a/yarvcore.h b/yarvcore.h
index 181e86d34e..ba99c8a2a5 100644
--- a/yarvcore.h
+++ b/yarvcore.h
@@ -410,6 +410,10 @@ struct rb_vm_tag {
     struct rb_vm_tag *prev;
 };
 
+struct rb_vm_trap_tag {
+    struct rb_vm_trap_tag *prev;
+};
+
 #define RUBY_VM_VALUE_CACHE_SIZE 0x1000
 #define USE_VALUE_CACHE 0
 
@@ -460,6 +464,7 @@ struct rb_thread_struct
     rb_thread_lock_t interrupt_lock;
 
     struct rb_vm_tag *tag;
+    struct rb_vm_trap_tag *trap_tag;
 
     int parse_in_eval;