diff --git a/src/shrpx.cc b/src/shrpx.cc
index 87bd9c28..24290891 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -2109,14 +2109,14 @@ void process_options(
     addr.host = ImmutableString::from_lit(DEFAULT_DOWNSTREAM_HOST);
     addr.port = DEFAULT_DOWNSTREAM_PORT;
 
-    DownstreamAddrGroup g("/");
+    DownstreamAddrGroup g(StringRef::from_lit("/"));
     g.addrs.push_back(std::move(addr));
-    mod_config()->router.add_route(g.pattern.get(), 1, addr_groups.size());
+    mod_config()->router.add_route(g.pattern.c_str(), 1, addr_groups.size());
     addr_groups.push_back(std::move(g));
   } else if (get_config()->http2_proxy || get_config()->client_proxy) {
     // We don't support host mapping in these cases.  Move all
     // non-catch-all patterns to catch-all pattern.
-    DownstreamAddrGroup catch_all("/");
+    DownstreamAddrGroup catch_all(StringRef::from_lit("/"));
     for (auto &g : addr_groups) {
       std::move(std::begin(g.addrs), std::end(g.addrs),
                 std::back_inserter(catch_all.addrs));
@@ -2124,7 +2124,7 @@ void process_options(
     std::vector<DownstreamAddrGroup>().swap(addr_groups);
     // maybe not necessary?
     mod_config()->router = Router();
-    mod_config()->router.add_route(catch_all.pattern.get(), 1,
+    mod_config()->router.add_route(catch_all.pattern.c_str(), 1,
                                    addr_groups.size());
     addr_groups.push_back(std::move(catch_all));
   }
@@ -2136,11 +2136,11 @@ void process_options(
   ssize_t catch_all_group = -1;
   for (size_t i = 0; i < addr_groups.size(); ++i) {
     auto &g = addr_groups[i];
-    if (util::streq(g.pattern.get(), "/")) {
+    if (g.pattern == "/") {
       catch_all_group = i;
     }
     if (LOG_ENABLED(INFO)) {
-      LOG(INFO) << "Host-path pattern: group " << i << ": '" << g.pattern.get()
+      LOG(INFO) << "Host-path pattern: group " << i << ": '" << g.pattern
                 << "'";
       for (auto &addr : g.addrs) {
         LOG(INFO) << "group " << i << " -> " << addr.host.c_str()
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 489885cf..23b480b3 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -78,21 +78,6 @@ TicketKeys::~TicketKeys() {
   }
 }
 
-DownstreamAddrGroup::DownstreamAddrGroup(const DownstreamAddrGroup &other)
-    : pattern(strcopy(other.pattern)), addrs(other.addrs) {}
-
-DownstreamAddrGroup &DownstreamAddrGroup::
-operator=(const DownstreamAddrGroup &other) {
-  if (this == &other) {
-    return *this;
-  }
-
-  pattern = strcopy(other.pattern);
-  addrs = other.addrs;
-
-  return *this;
-}
-
 namespace {
 int split_host_port(char *host, size_t hostlen, uint16_t *port_ptr,
                     const char *hostport, size_t hostportlen) {
@@ -612,7 +597,7 @@ void parse_mapping(const DownstreamAddr &addr, const char *src) {
       pattern += http2::normalize_path(slash, raw_pattern.second);
     }
     for (auto &g : addr_groups) {
-      if (g.pattern.get() == pattern) {
+      if (g.pattern == pattern) {
         g.addrs.push_back(addr);
         done = true;
         break;
@@ -621,10 +606,10 @@ void parse_mapping(const DownstreamAddr &addr, const char *src) {
     if (done) {
       continue;
     }
-    DownstreamAddrGroup g(pattern);
+    DownstreamAddrGroup g(StringRef{pattern});
     g.addrs.push_back(addr);
 
-    mod_config()->router.add_route(g.pattern.get(), strlen(g.pattern.get()),
+    mod_config()->router.add_route(g.pattern.c_str(), g.pattern.size(),
                                    addr_groups.size());
 
     addr_groups.push_back(std::move(g));
@@ -2529,7 +2514,7 @@ match_downstream_addr_group_host(const Router &router, const std::string &host,
     if (group != -1) {
       if (LOG_ENABLED(INFO)) {
         LOG(INFO) << "Found pattern with query " << host
-                  << ", matched pattern=" << groups[group].pattern.get();
+                  << ", matched pattern=" << groups[group].pattern;
       }
       return group;
     }
@@ -2546,7 +2531,7 @@ match_downstream_addr_group_host(const Router &router, const std::string &host,
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Found pattern with query " << host
                 << std::string(path, pathlen)
-                << ", matched pattern=" << groups[group].pattern.get();
+                << ", matched pattern=" << groups[group].pattern;
     }
     return group;
   }
@@ -2555,7 +2540,7 @@ match_downstream_addr_group_host(const Router &router, const std::string &host,
   if (group != -1) {
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Found pattern with query " << std::string(path, pathlen)
-                << ", matched pattern=" << groups[group].pattern.get();
+                << ", matched pattern=" << groups[group].pattern;
     }
     return group;
   }
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index c460cbc8..e024317a 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -301,13 +301,10 @@ struct DownstreamAddr {
 };
 
 struct DownstreamAddrGroup {
-  DownstreamAddrGroup(const std::string &pattern) : pattern(strcopy(pattern)) {}
-  DownstreamAddrGroup(const DownstreamAddrGroup &other);
-  DownstreamAddrGroup(DownstreamAddrGroup &&) = default;
-  DownstreamAddrGroup &operator=(const DownstreamAddrGroup &other);
-  DownstreamAddrGroup &operator=(DownstreamAddrGroup &&) = default;
+  DownstreamAddrGroup(const StringRef &pattern)
+      : pattern(pattern.c_str(), pattern.size()) {}
 
-  std::unique_ptr<char[]> pattern;
+  ImmutableString pattern;
   std::vector<DownstreamAddr> addrs;
 };
 
diff --git a/src/shrpx_config_test.cc b/src/shrpx_config_test.cc
index eda67e85..fa8c1391 100644
--- a/src/shrpx_config_test.cc
+++ b/src/shrpx_config_test.cc
@@ -256,7 +256,7 @@ void test_shrpx_config_match_downstream_addr_group(void) {
 
   for (size_t i = 0; i < groups.size(); ++i) {
     auto &g = groups[i];
-    router.add_route(g.pattern.get(), strlen(g.pattern.get()), i);
+    router.add_route(g.pattern.c_str(), g.pattern.size(), i);
   }
 
   CU_ASSERT(0 == match_downstream_addr_group(router, "nghttp2.org", "/", groups,