diff --git a/cmdedit.c b/cmdedit.c
index 981253db1..4f124d647 100644
--- a/cmdedit.c
+++ b/cmdedit.c
@@ -442,7 +442,8 @@ static void parse_prompt(const char *prmt_ptr)
 		if (flg_not_length == ']')
 			sub_len++;
 	}
-	free(pwd_buf);
+	if(pwd_buf!=(char *)unknown)
+		free(pwd_buf);
 	cmdedit_prompt = prmt_mem_ptr;
 	cmdedit_prmt_len = prmt_len - sub_len;
 	put_prompt();
diff --git a/shell/cmdedit.c b/shell/cmdedit.c
index 981253db1..4f124d647 100644
--- a/shell/cmdedit.c
+++ b/shell/cmdedit.c
@@ -442,7 +442,8 @@ static void parse_prompt(const char *prmt_ptr)
 		if (flg_not_length == ']')
 			sub_len++;
 	}
-	free(pwd_buf);
+	if(pwd_buf!=(char *)unknown)
+		free(pwd_buf);
 	cmdedit_prompt = prmt_mem_ptr;
 	cmdedit_prmt_len = prmt_len - sub_len;
 	put_prompt();