diff -urN squid-2.7.STABLE4.orig/src/client_side.c squid-2.7.STABLE4/src/client_side.c
--- squid-2.7.STABLE4.orig/src/client_side.c	2008-07-21 22:43:27.000000000 +0200
+++ squid-2.7.STABLE4/src/client_side.c	2008-09-18 12:51:05.169468168 +0200
@@ -1462,10 +1462,14 @@
 #if USE_USERAGENT_LOG
     if ((str = httpHeaderGetStr(req_hdr, HDR_USER_AGENT)))
 	logUserAgent(fqdnFromAddr(http->conn->log_addr), str);
+    else
+	logUserAgent(fqdnFromAddr(http->conn->log_addr), "-");
 #endif
 #if USE_REFERER_LOG
     if ((str = httpHeaderGetStr(req_hdr, HDR_REFERER)))
 	logReferer(fqdnFromAddr(http->conn->log_addr), str, rfc1738_escape_unescaped(http->uri));
+    else
+	logReferer(fqdnFromAddr(http->conn->log_addr), "-", rfc1738_escape_unescaped(http->uri));
 #endif
 #if FORW_VIA_DB
     if (httpHeaderHas(req_hdr, HDR_X_FORWARDED_FOR)) {