diff --git a/src/http2.cc b/src/http2.cc
index c5b596f4..64d700f0 100644
--- a/src/http2.cc
+++ b/src/http2.cc
@@ -1841,6 +1841,53 @@ StringRef normalize_path(BlockAllocator &balloc, const StringRef &path,
                    query);
 }
 
+StringRef normalize_path_colon(BlockAllocator &balloc, const StringRef &path,
+                               const StringRef &query) {
+  // First, decode %XX for unreserved characters and ':', then do
+  // http2::path_join
+
+  // We won't find %XX if length is less than 3.
+  if (path.size() < 3 ||
+      std::find(std::begin(path), std::end(path), '%') == std::end(path)) {
+    return path_join(balloc, StringRef{}, StringRef{}, path, query);
+  }
+
+  // includes last terminal NULL.
+  auto result = make_byte_ref(balloc, path.size() + 1);
+  auto p = result.base;
+
+  auto it = std::begin(path);
+  for (; it + 2 < std::end(path);) {
+    if (*it == '%') {
+      if (util::is_hex_digit(*(it + 1)) && util::is_hex_digit(*(it + 2))) {
+        auto c =
+            (util::hex_to_uint(*(it + 1)) << 4) + util::hex_to_uint(*(it + 2));
+        if (util::in_rfc3986_unreserved_chars(c) || c == ':') {
+          *p++ = c;
+
+          it += 3;
+
+          continue;
+        }
+        *p++ = '%';
+        *p++ = util::upcase(*(it + 1));
+        *p++ = util::upcase(*(it + 2));
+
+        it += 3;
+
+        continue;
+      }
+    }
+    *p++ = *it++;
+  }
+
+  p = std::copy(it, std::end(path), p);
+  *p = '\0';
+
+  return path_join(balloc, StringRef{}, StringRef{}, StringRef{result.base, p},
+                   query);
+}
+
 std::string normalize_path(const StringRef &path, const StringRef &query) {
   BlockAllocator balloc(1024, 1024);
 
diff --git a/src/http2.h b/src/http2.h
index b0b10651..f5c07136 100644
--- a/src/http2.h
+++ b/src/http2.h
@@ -410,6 +410,12 @@ StringRef to_method_string(int method_token);
 StringRef normalize_path(BlockAllocator &balloc, const StringRef &path,
                          const StringRef &query);
 
+// normalize_path_colon is like normalize_path, but it additionally
+// does percent-decoding %3A in order to workaround the issue that ':'
+// cannot be included in backend pattern.
+StringRef normalize_path_colon(BlockAllocator &balloc, const StringRef &path,
+                               const StringRef &query);
+
 std::string normalize_path(const StringRef &path, const StringRef &query);
 
 StringRef rewrite_clean_path(BlockAllocator &balloc, const StringRef &src);
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 363d564c..fa935cb6 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -1877,8 +1877,11 @@ Connections:
               affinity is enabled.
 
               Since ";" and ":" are  used as delimiter, <PATTERN> must
-              not  contain these  characters.  Since  ";" has  special
-              meaning in shell, the option value must be quoted.
+              not contain  these characters.  In order  to include ":"
+              in  <PATTERN>,  one  has  to  specify  "%3A"  (which  is
+              percent-encoded  from of  ":") instead.   Since ";"  has
+              special  meaning  in shell,  the  option  value must  be
+              quoted.
 
               Default: )"
       << DEFAULT_DOWNSTREAM_HOST << "," << DEFAULT_DOWNSTREAM_PORT << R"(
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 8f5cd507..6a097d43 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -1109,9 +1109,9 @@ int parse_mapping(Config *config, DownstreamAddrConfig &addr,
       *p = '\0';
       pattern = StringRef{iov.base, p};
     } else {
-      auto path = http2::normalize_path(downstreamconf.balloc,
-                                        StringRef{slash, std::end(raw_pattern)},
-                                        StringRef{});
+      auto path = http2::normalize_path_colon(
+          downstreamconf.balloc, StringRef{slash, std::end(raw_pattern)},
+          StringRef{});
       auto iov = make_byte_ref(downstreamconf.balloc,
                                std::distance(std::begin(raw_pattern), slash) +
                                    path.size() + 1);