diff --git a/cui.cpp b/cui.cpp
index 1e2bd14..f31ea20 100644
--- a/cui.cpp
+++ b/cui.cpp
@@ -91,7 +91,7 @@ std::string itoa(int i)
 std::string uid2username (uid_t uid)
 {
 	struct passwd * pwd = NULL;
-	errno = NULL;
+	errno = 0;
 
 	/* points to a static memory area, should not be freed */
 	pwd = getpwuid(uid);