diff --git a/ChangeLog b/ChangeLog
index 34933ec745..c087dce9b3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Sep 25 10:46:42 2001  Usaku Nakamura  <usa@ruby-lang.org>
+
+	* win32/win32.c (isInternalCmd): check return value of NtMakeCmdVector
+	  (Tietew <tietew@tietew.net>'s patch).
+
 Thu Sep 20 21:25:00 2001  Nobuyoshi Nakada  <nobu.nakada@nifty.ne.jp>
 
 	* eval.c (MATCH_DATA): access via rb_svar().
diff --git a/win32/win32.c b/win32/win32.c
index 52c361d27d..53c7c22467 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -367,20 +367,22 @@ static char *szInternalCmds[] = {
 int
 isInternalCmd(char *cmd)
 {
-        int i, fRet=0;
-	char **vec;
-        int vecc = NtMakeCmdVector(cmd, &vec, FALSE);
+    int i, fRet=0;
+    char **vec;
+    int vecc = NtMakeCmdVector(cmd, &vec, FALSE);
 
-        for( i = 0; szInternalCmds[i] ; i++){
-	    if(!strcasecmp(szInternalCmds[i], vec[0])){
-		fRet = 1;
-		break;
-	    }
-        }
- 
-	SafeFree (vec, vecc);
+    if (vecc == 0)
+	return 0;
+    for( i = 0; szInternalCmds[i] ; i++){
+	if(!strcasecmp(szInternalCmds[i], vec[0])){
+	    fRet = 1;
+	    break;
+	}
+    }
 
-	return fRet;
+    SafeFree(vec, vecc);
+
+    return fRet;
 }