diff --git a/include/atoms.xmacro b/include/atoms.xmacro
index b907f41e..af60b966 100644
--- a/include/atoms.xmacro
+++ b/include/atoms.xmacro
@@ -27,3 +27,4 @@ xmacro(I3_SOCKET_PATH)
 xmacro(I3_CONFIG_PATH)
 xmacro(I3_SYNC)
 xmacro(I3_SHMLOG_PATH)
+xmacro(I3_PID)
diff --git a/src/x.c b/src/x.c
index 65b3eb1f..84217a85 100644
--- a/src/x.c
+++ b/src/x.c
@@ -1030,9 +1030,11 @@ void x_set_name(Con *con, const char *name) {
  *
  */
 void x_set_i3_atoms(void) {
+    pid_t pid = getpid();
     xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_SOCKET_PATH, A_UTF8_STRING, 8,
                         (current_socketpath == NULL ? 0 : strlen(current_socketpath)),
                         current_socketpath);
+    xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_PID, XCB_ATOM_CARDINAL, 32, 1, &pid);
     xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_CONFIG_PATH, A_UTF8_STRING, 8,
                         strlen(current_configpath), current_configpath);
     xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_SHMLOG_PATH, A_UTF8_STRING, 8,