diff --git a/src/bin/dhcp4/dhcp4_srv.cc b/src/bin/dhcp4/dhcp4_srv.cc
index 744833e13c..13c363160d 100644
--- a/src/bin/dhcp4/dhcp4_srv.cc
+++ b/src/bin/dhcp4/dhcp4_srv.cc
@@ -221,7 +221,9 @@ Dhcpv4Exchange::Dhcpv4Exchange(const AllocEnginePtr& alloc_engine,
             CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
         const ClientClassDefListPtr& defs_ptr = dict->getClasses();
         for (auto def : *defs_ptr) {
-            context_->query_->classes_.erase(def->getName());
+            if (def->getMatchExpr()) {
+                context_->query_->classes_.erase(def->getName());
+            }
         }
         setReservedClientClasses(context_);
         evaluateClasses(context_->query_, false);
diff --git a/src/bin/dhcp6/dhcp6_srv.cc b/src/bin/dhcp6/dhcp6_srv.cc
index 95629d6fb6..bf80801b49 100644
--- a/src/bin/dhcp6/dhcp6_srv.cc
+++ b/src/bin/dhcp6/dhcp6_srv.cc
@@ -471,7 +471,9 @@ Dhcpv6Srv::initContext(const Pkt6Ptr& pkt,
             CfgMgr::instance().getCurrentCfg()->getClientClassDictionary();
         const ClientClassDefListPtr& defs_ptr = dict->getClasses();
         for (auto def : *defs_ptr) {
-            ctx.query_->classes_.erase(def->getName());
+            if (def->getMatchExpr()) {
+                ctx.query_->classes_.erase(def->getName());
+            }
         }
         setReservedClientClasses(pkt, ctx);
         evaluateClasses(pkt,  false);