diff --git a/ChangeLog b/ChangeLog
index 874804d95f..bcde6499fd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Apr 24 17:03:51 2012  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* win32/win32.c (waitpid): need to check the return value of
+	  FindChildSlotByHandle() before passing poll_child_status().
+	  this fixed a SEGV in test-all.  reported by ko1 via IRC.
+
 Tue Apr 24 16:04:39 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (parser_yylex): EXPR_BEG by keywords is a start point of
diff --git a/win32/win32.c b/win32/win32.c
index 7cbbaa2183..50387844ab 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -3921,6 +3921,7 @@ waitpid(rb_pid_t pid, int *stat_loc, int options)
 	int count = 0;
 	int ret;
 	HANDLE events[MAXCHILDNUM];
+	struct ChildRecord* cause;
 
 	FOREACH_CHILD(child) {
 	    if (!child->pid || child->pid < 0) continue;
@@ -3942,7 +3943,12 @@ waitpid(rb_pid_t pid, int *stat_loc, int options)
 	    return -1;
 	}
 
-	return poll_child_status(FindChildSlotByHandle(events[ret]), stat_loc);
+	cause = FindChildSlotByHandle(events[ret]);
+	if (!cause) {
+	    errno = ECHILD;
+	    return -1;
+	}
+	return poll_child_status(cause, stat_loc);
     }
     else {
 	struct ChildRecord* child = FindChildSlot(pid);