diff -urN squid-2.5.STABLE12/src/icap_respmod.c squid-2.5.STABLE12-closebeforesendfix/src/icap_respmod.c
--- squid-2.5.STABLE12/src/icap_respmod.c	2006-01-05 16:26:37.000000000 +0000
+++ squid-2.5.STABLE12-closebeforesendfix/src/icap_respmod.c	2006-01-05 16:52:42.000000000 +0000
@@ -252,6 +252,16 @@
 #endif
 
     if (icap->sc == 0) {
+        // http connection has been closed without sending us anything
+        if(len == 0 && theEnd == 1) {
+	    ErrorState *err;
+	    err = errorCon(ERR_INVALID_RESP, HTTP_BAD_GATEWAY);
+	    err->request = requestLink(icap->request);
+	    errorAppendEntry(icap->respmod.entry, err);
+	    comm_close(icap->icap_fd);
+	    return;
+        }
+
 	/* No data sent yet. Start with headers */
 	if ((icap->sc = buildRespModHeader(&mb, icap, buf, len, theEnd)) > 0) {
 	    buf += icap->sc;