diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index 33cb1225..d1e4c25d 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -910,17 +910,19 @@ ClientHandler::get_downstream_connection(Downstream *downstream) {
     //  have dealt with proxy case already, just use catch-all group.
     group_idx = catch_all;
   } else {
+    auto &balloc = downstream->get_block_allocator();
+
     if (!req.authority.empty()) {
-      group_idx = match_downstream_addr_group(routerconf, req.authority,
-                                              req.path, groups, catch_all);
+      group_idx = match_downstream_addr_group(
+          routerconf, req.authority, req.path, groups, catch_all, balloc);
     } else {
       auto h = req.fs.header(http2::HD_HOST);
       if (h) {
         group_idx = match_downstream_addr_group(routerconf, h->value, req.path,
-                                                groups, catch_all);
+                                                groups, catch_all, balloc);
       } else {
-        group_idx = match_downstream_addr_group(routerconf, StringRef{},
-                                                req.path, groups, catch_all);
+        group_idx = match_downstream_addr_group(
+            routerconf, StringRef{}, req.path, groups, catch_all, balloc);
       }
     }
   }
diff --git a/src/shrpx_worker.cc b/src/shrpx_worker.cc
index 3e7b47df..d5c6967f 100644
--- a/src/shrpx_worker.cc
+++ b/src/shrpx_worker.cc
@@ -459,7 +459,7 @@ size_t match_downstream_addr_group_host(
     const RouterConfig &routerconf, const StringRef &host,
     const StringRef &path,
     const std::vector<std::shared_ptr<DownstreamAddrGroup>> &groups,
-    size_t catch_all) {
+    size_t catch_all, BlockAllocator &balloc) {
 
   const auto &router = routerconf.router;
   const auto &rev_wildcard_router = routerconf.rev_wildcard_router;
@@ -492,12 +492,14 @@ size_t match_downstream_addr_group_host(
   }
 
   if (!wildcard_patterns.empty() && !host.empty()) {
-    auto rev_host_src = std::string{std::begin(host) + 1, std::end(host)};
-    std::reverse(std::begin(rev_host_src), std::end(rev_host_src));
+    auto rev_host_src = make_byte_ref(balloc, host.size() - 1);
+    auto ep =
+        std::copy(std::begin(host) + 1, std::end(host), rev_host_src.base);
+    std::reverse(rev_host_src.base, ep);
+    auto rev_host = StringRef{rev_host_src.base, ep};
 
     ssize_t best_group = -1;
     const RNode *last_node = nullptr;
-    auto rev_host = StringRef{std::begin(rev_host_src), std::end(rev_host_src)};
 
     for (;;) {
       size_t nread = 0;
@@ -548,7 +550,7 @@ size_t match_downstream_addr_group(
     const RouterConfig &routerconf, const StringRef &hostport,
     const StringRef &raw_path,
     const std::vector<std::shared_ptr<DownstreamAddrGroup>> &groups,
-    size_t catch_all) {
+    size_t catch_all, BlockAllocator &balloc) {
   if (std::find(std::begin(hostport), std::end(hostport), '/') !=
       std::end(hostport)) {
     // We use '/' specially, and if '/' is included in host, it breaks
@@ -562,7 +564,7 @@ size_t match_downstream_addr_group(
 
   if (hostport.empty()) {
     return match_downstream_addr_group_host(routerconf, hostport, path, groups,
-                                            catch_all);
+                                            catch_all, balloc);
   }
 
   StringRef host;
@@ -584,16 +586,17 @@ size_t match_downstream_addr_group(
     host = StringRef{std::begin(hostport), p};
   }
 
-  std::string low_host;
   if (std::find_if(std::begin(host), std::end(host), [](char c) {
         return 'A' <= c || c <= 'Z';
       }) != std::end(host)) {
-    low_host = host.str();
-    util::inp_strlower(low_host);
-    host = StringRef{low_host};
+    auto low_host = make_byte_ref(balloc, host.size() + 1);
+    auto ep = std::copy(std::begin(host), std::end(host), low_host.base);
+    *ep = '\0';
+    util::inp_strlower(low_host.base, ep);
+    host = StringRef{low_host.base, ep};
   }
   return match_downstream_addr_group_host(routerconf, host, path, groups,
-                                          catch_all);
+                                          catch_all, balloc);
 }
 
 void downstream_failure(DownstreamAddr *addr) {
diff --git a/src/shrpx_worker.h b/src/shrpx_worker.h
index 7e506029..c729af1e 100644
--- a/src/shrpx_worker.h
+++ b/src/shrpx_worker.h
@@ -283,7 +283,7 @@ size_t match_downstream_addr_group(
     const RouterConfig &routerconfig, const StringRef &hostport,
     const StringRef &path,
     const std::vector<std::shared_ptr<DownstreamAddrGroup>> &groups,
-    size_t catch_all);
+    size_t catch_all, BlockAllocator &balloc);
 
 void downstream_failure(DownstreamAddr *addr);
 
diff --git a/src/shrpx_worker_test.cc b/src/shrpx_worker_test.cc
index 5294433f..2e419416 100644
--- a/src/shrpx_worker_test.cc
+++ b/src/shrpx_worker_test.cc
@@ -49,6 +49,7 @@ void test_shrpx_worker_match_downstream_addr_group(void) {
     groups.push_back(std::move(g));
   }
 
+  BlockAllocator balloc(1024, 1024);
   RouterConfig routerconf;
 
   auto &router = routerconf.router;
@@ -62,122 +63,129 @@ void test_shrpx_worker_match_downstream_addr_group(void) {
 
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/"), groups, 255));
+                     StringRef::from_lit("/"), groups, 255, balloc));
 
   // port is removed
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org:8080"),
-                     StringRef::from_lit("/"), groups, 255));
+                     StringRef::from_lit("/"), groups, 255, balloc));
 
   // host is case-insensitive
   CU_ASSERT(4 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("WWW.nghttp2.org"),
-                     StringRef::from_lit("/alpha"), groups, 255));
+                     StringRef::from_lit("/alpha"), groups, 255, balloc));
 
   CU_ASSERT(1 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo/"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo/"), groups, 255,
+                     balloc));
 
   // /alpha/bravo also matches /alpha/bravo/
   CU_ASSERT(1 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
 
   // path part is case-sensitive
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/Alpha/bravo"), groups, 255));
+                     StringRef::from_lit("/Alpha/bravo"), groups, 255, balloc));
 
   CU_ASSERT(1 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo/charlie"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo/charlie"), groups, 255,
+                     balloc));
 
   CU_ASSERT(2 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/charlie"), groups, 255));
+                     StringRef::from_lit("/alpha/charlie"), groups, 255,
+                     balloc));
 
   // pattern which does not end with '/' must match its entirely.  So
   // this matches to group 0, not group 2.
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/charlie/"), groups, 255));
+                     StringRef::from_lit("/alpha/charlie/"), groups, 255,
+                     balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("example.org"),
-                       StringRef::from_lit("/"), groups, 255));
-
-  CU_ASSERT(255 ==
-            match_downstream_addr_group(routerconf, StringRef::from_lit(""),
-                                        StringRef::from_lit("/"), groups, 255));
+                       StringRef::from_lit("/"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit(""),
-                       StringRef::from_lit("alpha"), groups, 255));
+                       StringRef::from_lit("/"), groups, 255, balloc));
+
+  CU_ASSERT(255 == match_downstream_addr_group(
+                       routerconf, StringRef::from_lit(""),
+                       StringRef::from_lit("alpha"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("foo/bar"),
-                       StringRef::from_lit("/"), groups, 255));
+                       StringRef::from_lit("/"), groups, 255, balloc));
 
   // If path is StringRef::from_lit("*", only match with host + "/").
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("*"), groups, 255));
+                     StringRef::from_lit("*"), groups, 255, balloc));
 
-  CU_ASSERT(
-      5 == match_downstream_addr_group(routerconf, StringRef::from_lit("[::1]"),
-                                       StringRef::from_lit("/"), groups, 255));
+  CU_ASSERT(5 == match_downstream_addr_group(
+                     routerconf, StringRef::from_lit("[::1]"),
+                     StringRef::from_lit("/"), groups, 255, balloc));
   CU_ASSERT(5 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("[::1]:8080"),
-                     StringRef::from_lit("/"), groups, 255));
-  CU_ASSERT(255 ==
-            match_downstream_addr_group(routerconf, StringRef::from_lit("[::1"),
-                                        StringRef::from_lit("/"), groups, 255));
+                     StringRef::from_lit("/"), groups, 255, balloc));
+  CU_ASSERT(255 == match_downstream_addr_group(
+                       routerconf, StringRef::from_lit("[::1"),
+                       StringRef::from_lit("/"), groups, 255, balloc));
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("[::1]8000"),
-                       StringRef::from_lit("/"), groups, 255));
+                       StringRef::from_lit("/"), groups, 255, balloc));
 
   // Check the case where adding route extends tree
   CU_ASSERT(6 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo/delta"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo/delta"), groups, 255,
+                     balloc));
 
   CU_ASSERT(1 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo/delta/"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo/delta/"), groups, 255,
+                     balloc));
 
   // Check the case where query is done in a single node
   CU_ASSERT(7 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("example.com"),
-                     StringRef::from_lit("/alpha/bravo"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("example.com"),
-                       StringRef::from_lit("/alpha/bravo/"), groups, 255));
+                       StringRef::from_lit("/alpha/bravo/"), groups, 255,
+                       balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("example.com"),
-                       StringRef::from_lit("/alpha"), groups, 255));
+                       StringRef::from_lit("/alpha"), groups, 255, balloc));
 
   // Check the case where quey is done in a single node
   CU_ASSERT(8 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("192.168.0.1"),
-                     StringRef::from_lit("/alpha"), groups, 255));
+                     StringRef::from_lit("/alpha"), groups, 255, balloc));
 
   CU_ASSERT(8 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("192.168.0.1"),
-                     StringRef::from_lit("/alpha/"), groups, 255));
+                     StringRef::from_lit("/alpha/"), groups, 255, balloc));
 
   CU_ASSERT(8 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("192.168.0.1"),
-                     StringRef::from_lit("/alpha/bravo"), groups, 255));
+                     StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("192.168.0.1"),
-                       StringRef::from_lit("/alph"), groups, 255));
+                       StringRef::from_lit("/alph"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit("192.168.0.1"),
-                       StringRef::from_lit("/"), groups, 255));
+                       StringRef::from_lit("/"), groups, 255, balloc));
 
   // Test for wildcard hosts
   auto g1 = std::make_shared<DownstreamAddrGroup>();
@@ -199,27 +207,28 @@ void test_shrpx_worker_match_downstream_addr_group(void) {
 
   CU_ASSERT(11 == match_downstream_addr_group(
                       routerconf, StringRef::from_lit("git.nghttp2.org"),
-                      StringRef::from_lit("/echo"), groups, 255));
+                      StringRef::from_lit("/echo"), groups, 255, balloc));
 
   CU_ASSERT(10 == match_downstream_addr_group(
                       routerconf, StringRef::from_lit("0git.nghttp2.org"),
-                      StringRef::from_lit("/echo"), groups, 255));
+                      StringRef::from_lit("/echo"), groups, 255, balloc));
 
   CU_ASSERT(11 == match_downstream_addr_group(
                       routerconf, StringRef::from_lit("it.nghttp2.org"),
-                      StringRef::from_lit("/echo"), groups, 255));
+                      StringRef::from_lit("/echo"), groups, 255, balloc));
 
   CU_ASSERT(255 == match_downstream_addr_group(
                        routerconf, StringRef::from_lit(".nghttp2.org"),
-                       StringRef::from_lit("/echo/foxtrot"), groups, 255));
+                       StringRef::from_lit("/echo/foxtrot"), groups, 255,
+                       balloc));
 
   CU_ASSERT(9 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("alpha.nghttp2.org"),
-                     StringRef::from_lit("/golf"), groups, 255));
+                     StringRef::from_lit("/golf"), groups, 255, balloc));
 
   CU_ASSERT(0 == match_downstream_addr_group(
                      routerconf, StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/echo"), groups, 255));
+                     StringRef::from_lit("/echo"), groups, 255, balloc));
 }
 
 } // namespace shrpx