Index: src/ICAP/ICAPModXact.cc
===================================================================
RCS file: /cvsroot/squid/squid3/src/ICAP/ICAPModXact.cc,v
retrieving revision 1.1.2.17
diff -u -u -r1.1.2.17 ICAPModXact.cc
--- src/ICAP/ICAPModXact.cc	25 Oct 2006 04:57:03 -0000	1.1.2.17
+++ src/ICAP/ICAPModXact.cc	6 Dec 2006 15:12:22 -0000
@@ -1067,10 +1067,11 @@
     // cannot preview more than we can backup
     size_t ad = XMIN(wantedSize, TheBackupLimit);
 
-    if (virginBody.expected() && virginBody.knownSize())
-        ad = XMIN(ad, virginBody.size()); // not more than we have
+    if (!virginBody.expected())
+        ad = 0; // nothing to preview but headers
     else
-        ad = 0; // questionable optimization?
+    if (virginBody.knownSize())
+        ad = XMIN(ad, virginBody.size()); // not more than we have
 
     debugs(93, 5, "ICAPModXact should offer " << ad << "-byte preview " <<
            "(service wanted " << wantedSize << ")");