diff -up sudo-1.8.6p3/plugins/sudoers/match.c.netgrmatchtrace sudo-1.8.6p3/plugins/sudoers/match.c
--- sudo-1.8.6p3/plugins/sudoers/match.c.netgrmatchtrace	2013-08-12 14:42:56.498247674 +0200
+++ sudo-1.8.6p3/plugins/sudoers/match.c	2013-08-12 14:43:01.009264127 +0200
@@ -713,6 +713,10 @@ netgr_matches(char *netgr, char *lhost,
 #ifdef HAVE_GETDOMAINNAME
     static int initialized;
 #endif
+#ifdef HAVE_INNETGR
+    bool innetgr_lhost = false;
+    bool innetgr_shost = false;
+#endif
     debug_decl(netgr_matches, SUDO_DEBUG_MATCH)
 
     /* make sure we have a valid netgroup, sudo style */
@@ -733,9 +737,39 @@ netgr_matches(char *netgr, char *lhost,
 
 #ifdef HAVE_INNETGR
     if (innetgr(netgr, lhost, user, domain))
-	debug_return_bool(true);
+	    innetgr_lhost = true;
     else if (lhost != shost && innetgr(netgr, shost, user, domain))
-	debug_return_bool(true);
+	    innetgr_shost = true;
+
+    if (innetgr_lhost) {
+	    sudo_debug_printf(SUDO_DEBUG_TRACE,
+	                      "(%s, %s, %s) found in netgroup %s\n",
+	                      shost ? shost : "*",
+	                      user ? user : "*",
+	                      domain ? domain : "*",
+	                      netgr);
+    } else if (innetgr_shost) {
+	    sudo_debug_printf(SUDO_DEBUG_TRACE,
+	                      "(%s, %s, %s) found in netgroup %s\n",
+	                      lhost ? lhost : "*",
+	                      user ? user : "*",
+	                      domain ? domain : "*",
+	                      netgr);
+    } else {
+	    sudo_debug_printf(SUDO_DEBUG_TRACE,
+	                      "(%s, %s, %s) NOT found in netgroup %s\n",
+	                      shost ? shost : "*",
+	                      user ? user : "*",
+	                      domain ? domain : "*",
+	                      netgr);
+	    sudo_debug_printf(SUDO_DEBUG_TRACE,
+	                      "(%s, %s, %s) NOT found in netgroup %s\n",
+	                      lhost ? lhost : "*",
+	                      user ? user : "*",
+	                      domain ? domain : "*",
+	                      netgr);
+    }
+    debug_return_bool(innetgr_lhost || innetgr_shost);
 #endif /* HAVE_INNETGR */
 
     debug_return_bool(false);