diff --git a/gennghttpxfun.py b/gennghttpxfun.py
index 172d9f03..1f4d9b79 100755
--- a/gennghttpxfun.py
+++ b/gennghttpxfun.py
@@ -165,6 +165,7 @@ OPTIONS = [
     "single-thread",
     "add-x-forwarded-proto",
     "strip-incoming-x-forwarded-proto",
+    "single-process",
 ]
 
 LOGVARS = [
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 38594155..683e7ad8 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -1205,13 +1205,17 @@ pid_t fork_worker_process(int &main_ipc_fd,
     return -1;
   }
 
-  auto pid = fork();
+  auto config = get_config();
+
+  pid_t pid = 0;
+
+  if (!config->single_process) {
+    pid = fork();
+  }
 
   if (pid == 0) {
     ev_loop_fork(EV_DEFAULT);
 
-    auto config = get_config();
-
     for (auto &addr : config->conn.listener.addrs) {
       util::make_socket_closeonexec(addr.fd);
     }
@@ -1230,22 +1234,37 @@ pid_t fork_worker_process(int &main_ipc_fd,
       LOG(FATAL) << "Unblocking all signals failed: "
                  << xsi_strerror(error, errbuf.data(), errbuf.size());
 
-      nghttp2_Exit(EXIT_FAILURE);
+      if (config->single_process) {
+        exit(EXIT_FAILURE);
+      } else {
+        nghttp2_Exit(EXIT_FAILURE);
+      }
+    }
+
+    if (!config->single_process) {
+      close(ipc_fd[1]);
     }
 
-    close(ipc_fd[1]);
     WorkerProcessConfig wpconf{ipc_fd[0]};
     rv = worker_process_event_loop(&wpconf);
     if (rv != 0) {
       LOG(FATAL) << "Worker process returned error";
 
-      nghttp2_Exit(EXIT_FAILURE);
+      if (config->single_process) {
+        exit(EXIT_FAILURE);
+      } else {
+        nghttp2_Exit(EXIT_FAILURE);
+      }
     }
 
     LOG(NOTICE) << "Worker process shutting down momentarily";
 
     // call exit(...) instead of nghttp2_Exit to get leak sanitizer report
-    nghttp2_Exit(EXIT_SUCCESS);
+    if (config->single_process) {
+      exit(EXIT_SUCCESS);
+    } else {
+      nghttp2_Exit(EXIT_SUCCESS);
+    }
   }
 
   // parent process
@@ -1322,7 +1341,7 @@ int event_loop() {
 
   auto loop = ev_default_loop(config->ev_loop_flags);
 
-  int ipc_fd;
+  int ipc_fd = 0;
 
   auto pid = fork_worker_process(ipc_fd, {});
 
@@ -2641,6 +2660,14 @@ Process:
   --user=<USER>
               Run this program as <USER>.   This option is intended to
               be used to drop root privileges.
+  --single-process
+              Run this program in a  single process mode for debugging
+              purpose.  Without this option,  nghttpx creates at least
+              2  processes:  master  and worker  processes.   If  this
+              option is  used, master  and worker  are unified  into a
+              single process.  nghttpx still spawns additional process
+              if neverbleed is used.  In  the single process mode, the
+              signal handling feature is disabled.
 
 Scripting:
   --mruby-file=<PATH>
@@ -3000,7 +3027,7 @@ void reload_config(WorkerProcess *wp) {
   // already created first default loop.
   auto loop = ev_default_loop(new_config->ev_loop_flags);
 
-  int ipc_fd;
+  int ipc_fd = 0;
 
   // fork_worker_process and forked child process assumes new
   // configuration can be obtained from get_config().
@@ -3309,6 +3336,7 @@ int main(int argc, char **argv) {
         {SHRPX_OPT_ADD_X_FORWARDED_PROTO.c_str(), no_argument, &flag, 157},
         {SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO.c_str(), no_argument, &flag,
          158},
+        {SHRPX_OPT_SINGLE_PROCESS.c_str(), no_argument, &flag, 159},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -4055,6 +4083,11 @@ int main(int argc, char **argv) {
         cmdcfgs.emplace_back(SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO,
                              StringRef::from_lit("yes"));
         break;
+      case 159:
+        // --single-process
+        cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_PROCESS,
+                             StringRef::from_lit("yes"));
+        break;
       default:
         break;
       }
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index 8914a63c..6e41acb6 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -1620,6 +1620,9 @@ int option_lookup_token(const char *name, size_t namelen) {
       if (util::strieq_l("client-cipher", name, 13)) {
         return SHRPX_OPTID_CLIENT_CIPHERS;
       }
+      if (util::strieq_l("single-proces", name, 13)) {
+        return SHRPX_OPTID_SINGLE_PROCESS;
+      }
       break;
     case 't':
       if (util::strieq_l("tls-proto-lis", name, 13)) {
@@ -3374,6 +3377,10 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_PROTO:
     config->http.xfp.strip_incoming = util::strieq_l("yes", optarg);
 
+    return 0;
+  case SHRPX_OPTID_SINGLE_PROCESS:
+    config->single_process = util::strieq_l("yes", optarg);
+
     return 0;
   case SHRPX_OPTID_CONF:
     LOG(WARN) << "conf: ignored";
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index ba6f0cf2..251ece69 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -340,6 +340,7 @@ constexpr auto SHRPX_OPT_ADD_X_FORWARDED_PROTO =
     StringRef::from_lit("add-x-forwarded-proto");
 constexpr auto SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_PROTO =
     StringRef::from_lit("strip-incoming-x-forwarded-proto");
+constexpr auto SHRPX_OPT_SINGLE_PROCESS = StringRef::from_lit("single-process");
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
@@ -872,6 +873,7 @@ struct Config {
         verbose{false},
         daemon{false},
         http2_proxy{false},
+        single_process{false},
         single_thread{false},
         ev_loop_flags{0} {}
   ~Config();
@@ -913,6 +915,9 @@ struct Config {
   bool verbose;
   bool daemon;
   bool http2_proxy;
+  // Run nghttpx in single process mode.  With this mode, signal
+  // handling is omitted.
+  bool single_process;
   bool single_thread;
   // flags passed to ev_default_loop() and ev_loop_new()
   int ev_loop_flags;
@@ -1049,6 +1054,7 @@ enum {
   SHRPX_OPTID_RESPONSE_HEADER_FIELD_BUFFER,
   SHRPX_OPTID_RLIMIT_NOFILE,
   SHRPX_OPTID_SERVER_NAME,
+  SHRPX_OPTID_SINGLE_PROCESS,
   SHRPX_OPTID_SINGLE_THREAD,
   SHRPX_OPTID_STREAM_READ_TIMEOUT,
   SHRPX_OPTID_STREAM_WRITE_TIMEOUT,