diff --git a/ChangeLog b/ChangeLog
index 260960950e..33265581ae 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Jun 13 13:03:08 2005  Hirokazu Yamamoto  <ocean@m2.ccsnet.ne.jp>
+
+	* hash.c (ruby_setenv): fixed SEGV. [ruby-dev:26186]
+
 Mon Jun 13 01:54:20 2005  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* signal.c (sigexit): call rb_thread_signal_exit() instead of
diff --git a/hash.c b/hash.c
index 88b060f11a..05491f0d9d 100644
--- a/hash.c
+++ b/hash.c
@@ -1824,27 +1824,24 @@ ruby_setenv(name, value)
 	tmpenv[max] = 0;
 	environ = tmpenv;		/* tell exec where it is now */
     }
-    if (!value) {
-	if (environ != origenviron) {
+    if (environ[i]) {
 	char **envp = origenviron;
 	while (*envp && *envp != environ[i]) envp++;
 	if (!*envp)
 	    free(environ[i]);
-	}
+	if (!value) {
 	    while (environ[i]) {
 		environ[i] = environ[i+1];
 		i++;
 	    }
 	    return;
 	}
-    if (!environ[i]) {			/* does not exist yet */
+    }
+    else {			/* does not exist yet */
+	if (!value) return;
 	REALLOC_N(environ, char*, i+2);	/* just expand it a bit */
 	environ[i+1] = 0;	/* make sure it's null terminated */
     }
-    else {
-	if (environ[i] != origenviron[i])
-	    free(environ[i]);
-    }
     environ[i] = ALLOC_N(char, strlen(name) + strlen(value) + 2);
 #ifndef MSDOS
     sprintf(environ[i],"%s=%s",name,value); /* all that work just for this */