diff --git a/reg-tests/cache/if-modified-since.vtc b/reg-tests/cache/if-modified-since.vtc
index e491e46..8ae1cce 100644
--- a/reg-tests/cache/if-modified-since.vtc
+++ b/reg-tests/cache/if-modified-since.vtc
@@ -40,6 +40,12 @@
 } -start
 
 haproxy h1 -conf {
+       global
+               # WT: limit false-positives causing "HTTP header incomplete" due to
+               # idle server connections being randomly used and randomly expiring
+               # under us.
+               tune.idle-pool.shared off
+
        defaults
                mode http
                ${no-htx} option http-use-htx