diff --git a/fake_lib/README.md b/fake_lib/README.md
index 0b8c76d9..3ceb1a91 100644
--- a/fake_lib/README.md
+++ b/fake_lib/README.md
@@ -65,13 +65,14 @@ export FAKE_EC_HOMEDIR=/tmp/FakeEtherCAT
 rm -rf $FAKE_EC_HOMEDIR
 mkdir -p $FAKE_EC_HOMEDIR
 ```
+For each master instance, one subdirectory named by the master id is created.
 
 ### Spin up your application
 
 Now it's time to simply launch your application.
 You will notice that the PDO configuration will be dumped at stderr.
 The path displayed is the path of the RtIPC variable in the following format:
-`$FAKE_EC_PREFIX/$MASTER_ID/$DOMAIN_ID/$ALIAS$POSITION/$PDO`.
+`$FAKE_EC_PREFIX/$MASTER_ID/$ALIAS$POSITION/$PDO`.
 
 ## How to emulate EtherCAT slaves
 
diff --git a/fake_lib/fakeethercat.cpp b/fake_lib/fakeethercat.cpp
index b60b1994..ca588db8 100644
--- a/fake_lib/fakeethercat.cpp
+++ b/fake_lib/fakeethercat.cpp
@@ -30,6 +30,7 @@
 #include <unordered_set>
 #include <iterator>
 #include <ios>
+#include <sys/stat.h>
 
 static std::ostream &operator<<(std::ostream &os, const sdo_address &a)
 {
@@ -105,7 +106,7 @@ ec_domain::ec_domain(rtipc *rtipc, const char *prefix, ec_master_t *master) : rt
 {
 }
 
-int ec_domain::activate(int domain_id)
+int ec_domain::activate()
 {
     std::unordered_set<uint32_t> slaves;
 
@@ -211,6 +212,12 @@ int ecrt_domain_state(
 
 int ec_master::activate()
 {
+    for (auto &domain : domains)
+    {
+        if (domain.activate())
+            return -1;
+    }
+
     {
         std::ofstream out(rt_ipc_dir + "/" + rt_ipc_name + "_slaves.json");
         if (!out.is_open())
@@ -414,16 +421,40 @@ static const char *getName()
     return "FakeEtherCAT";
 }
 
-static const char *getRtIpcDir()
+static int mkpath(const std::string &file_path)
 {
-    if (const auto ans = getenv("FAKE_EC_HOMEDIR"))
+    if (file_path.empty())
+        return 0;
+
+    std::size_t offset = 0;
+    do
     {
-        return ans;
-    }
-    return "/tmp/FakeEtherCAT";
+        offset = file_path.find('/', offset + 1);
+        const auto subpath = file_path.substr(0, offset);
+        if (mkdir(subpath.c_str(), 0755) == -1)
+        {
+            if (errno != EEXIST)
+            {
+                return -1;
+            }
+        }
+    } while (offset != std::string::npos);
+    return 0;
 }
 
-ec_master::ec_master(int id) : rt_ipc_dir(getRtIpcDir()), rt_ipc_name(getName()), rt_ipc(rtipc_create(rt_ipc_name.c_str(), rt_ipc_dir.c_str())), id_(id)
+static std::string getRtIpcDir(int idx)
+{
+    std::string ans;
+    if (const auto e = getenv("FAKE_EC_HOMEDIR"))
+    {
+        ans = e + std::string("/") + std::to_string(idx);
+    }
+    ans = "/tmp/FakeEtherCAT/" + std::to_string(idx);
+    mkpath(ans);
+    return ans;
+}
+
+ec_master::ec_master(int id) : rt_ipc_dir(getRtIpcDir(id)), rt_ipc_name(getName()), rt_ipc(rtipc_create(rt_ipc_name.c_str(), rt_ipc_dir.c_str())), id_(id)
 {
 }
 
diff --git a/fake_lib/fakeethercat.h b/fake_lib/fakeethercat.h
index 71bd21dc..ff83dbd2 100644
--- a/fake_lib/fakeethercat.h
+++ b/fake_lib/fakeethercat.h
@@ -180,7 +180,7 @@ public:
         return const_cast<uint8_t *>(data.data());
     }
 
-    int activate(int domain_id);
+    int activate();
     int process();
     int queue();