diff --git a/src/libstore/include/nix/store/ssh.hh b/src/libstore/include/nix/store/ssh.hh
index 574cb5cf414..03a67c45472 100644
--- a/src/libstore/include/nix/store/ssh.hh
+++ b/src/libstore/include/nix/store/ssh.hh
@@ -39,8 +39,8 @@ private:
 
     Sync<State> state_;
 
-    void addCommonSSHOpts(Strings & args);
-    bool isMasterRunning();
+    void addCommonSSHOpts(Strings & args, Path socketPath);
+    bool isMasterRunning(Path socketPath);
 
 #ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
     Path startMaster();
diff --git a/src/libstore/ssh.cc b/src/libstore/ssh.cc
index 1a99083669c..e8309e75b27 100644
--- a/src/libstore/ssh.cc
+++ b/src/libstore/ssh.cc
@@ -89,7 +89,7 @@ SSHMaster::SSHMaster(
     checkValidAuthority(authority);
 }
 
-void SSHMaster::addCommonSSHOpts(Strings & args)
+void SSHMaster::addCommonSSHOpts(Strings & args, Path socketPath)
 {
     auto sshArgs = getNixSshOpts();
     args.insert(args.end(), sshArgs.begin(), sshArgs.end());
@@ -113,12 +113,15 @@ void SSHMaster::addCommonSSHOpts(Strings & args)
     // the remote session won't be garbled if the local command is slow.
     args.push_back("-oPermitLocalCommand=yes");
     args.push_back("-oLocalCommand=echo started");
+    args.insert(args.end(), {"-S", socketPath});
 }
 
-bool SSHMaster::isMasterRunning()
+bool SSHMaster::isMasterRunning(Path socketPath)
 {
+    assert(useMaster);
+
     Strings args = {"-O", "check", hostnameAndUser};
-    addCommonSSHOpts(args);
+    addCommonSSHOpts(args, socketPath);
 
     auto res = runProgram(RunOptions{.program = "ssh", .args = args, .mergeStderrToStdout = true});
     return res.first == 0;
@@ -183,9 +186,7 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(Strings && comman
 
             if (!fakeSSH) {
                 args = {"ssh", hostnameAndUser.c_str(), "-x"};
-                addCommonSSHOpts(args);
-                if (socketPath != "")
-                    args.insert(args.end(), {"-S", socketPath});
+                addCommonSSHOpts(args, socketPath);
                 if (verbosity >= lvlChatty)
                     args.push_back("-v");
                 args.splice(args.end(), std::move(extraSshArgs));
@@ -206,7 +207,7 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(Strings && comman
 
     // Wait for the SSH connection to be established,
     // So that we don't overwrite the password prompt with our progress bar.
-    if (!fakeSSH && !useMaster && !isMasterRunning()) {
+    if (!fakeSSH && !(useMaster && isMasterRunning(socketPath))) {
         std::string reply;
         try {
             reply = readLine(out.readSide.get());
@@ -231,7 +232,7 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(Strings && comman
 Path SSHMaster::startMaster()
 {
     if (!useMaster)
-        return "";
+        return "none";
 
     auto state(state_.lock());
 
@@ -248,7 +249,7 @@ Path SSHMaster::startMaster()
 
     auto suspension = logger->suspend();
 
-    if (isMasterRunning())
+    if (isMasterRunning(state->socketPath))
         return state->socketPath;
 
     state->sshMaster = startProcess(
@@ -260,10 +261,10 @@ Path SSHMaster::startMaster()
             if (dup2(out.writeSide.get(), STDOUT_FILENO) == -1)
                 throw SysError("duping over stdout");
 
-            Strings args = {"ssh", hostnameAndUser.c_str(), "-M", "-N", "-S", state->socketPath};
+            Strings args = {"ssh", hostnameAndUser.c_str(), "-M", "-N"};
             if (verbosity >= lvlChatty)
                 args.push_back("-v");
-            addCommonSSHOpts(args);
+            addCommonSSHOpts(args, state->socketPath);
             auto env = createSSHEnv();
             nix::execvpe(args.begin()->c_str(), stringsToCharPtrs(args).data(), stringsToCharPtrs(env).data());