diff --git a/bar.c b/bar.c
index c839567..2a84a3b 100644
--- a/bar.c
+++ b/bar.c
@@ -10,6 +10,8 @@
 #include <poll.h>
 #include <signal.h>
 
+#include <sys/eventfd.h>
+
 #include <xcb/xcb.h>
 #include <xcb/xcb_event.h>
 #include <xcb/randr.h>
@@ -383,10 +385,14 @@ run(struct bar_run_context *run_ctx)
     struct module_run_context run_ctx_center[bar->center.count];
     struct module_run_context run_ctx_right[bar->right.count];
 
+    int ready_fd = eventfd(0, EFD_SEMAPHORE);
+    assert(ready_fd != -1);
+
     for (size_t i = 0; i < bar->left.count; i++) {
         struct module_run_context *ctx = &run_ctx_left[i];
 
         ctx->module = bar->left.mods[i];
+        ctx->ready_fd = ready_fd;
         ctx->abort_fd = run_ctx->abort_fd;
 
         thrd_create(&thrd_left[i], (int (*)(void *))bar->left.mods[i]->run, ctx);
@@ -395,6 +401,7 @@ run(struct bar_run_context *run_ctx)
         struct module_run_context *ctx = &run_ctx_center[i];
 
         ctx->module = bar->center.mods[i];
+        ctx->ready_fd = ready_fd;
         ctx->abort_fd = run_ctx->abort_fd;
 
         thrd_create(&thrd_center[i], (int (*)(void *))bar->center.mods[i]->run, ctx);
@@ -403,12 +410,20 @@ run(struct bar_run_context *run_ctx)
         struct module_run_context *ctx = &run_ctx_right[i];
 
         ctx->module = bar->right.mods[i];
+        ctx->ready_fd = ready_fd;
         ctx->abort_fd = run_ctx->abort_fd;
 
         thrd_create(&thrd_right[i], (int (*)(void *))bar->right.mods[i]->run, ctx);
     }
 
-    LOG_DBG("modules started");
+    LOG_DBG("waiting for modules to become ready");
+    for (size_t i = 0; i < bar->left.count + bar->center.count + bar->right.count; i++) {
+        uint64_t b;
+        read(ready_fd, &b, sizeof(b));
+    }
+
+    close(ready_fd);
+    LOG_DBG("all modules started");
 
     int fd = xcb_get_file_descriptor(bar->conn);
 
diff --git a/module.h b/module.h
index 18314fc..2bb12bd 100644
--- a/module.h
+++ b/module.h
@@ -11,6 +11,7 @@ struct module;
 
 struct module_run_context {
     struct module *module;
+    int ready_fd;
     int abort_fd;
 };
 
diff --git a/modules/battery/battery.c b/modules/battery/battery.c
index 3792ea2..61cacee 100644
--- a/modules/battery/battery.c
+++ b/modules/battery/battery.c
@@ -2,6 +2,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 #include <unistd.h>
 #include <assert.h>
@@ -202,6 +203,8 @@ run(struct module_run_context *ctx)
     udev_monitor_filter_add_match_subsystem_devtype(mon, "power_supply", NULL);
     udev_monitor_enable_receiving(mon);
 
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
+
     bool first = true;
     while (true) {
         if (!first) {
diff --git a/modules/clock/clock.c b/modules/clock/clock.c
index 4680a03..5e4ca46 100644
--- a/modules/clock/clock.c
+++ b/modules/clock/clock.c
@@ -1,6 +1,8 @@
 #include "clock.h"
 #include <stdlib.h>
+#include <stdint.h>
 #include <time.h>
+#include <unistd.h>
 #include <assert.h>
 
 #include <poll.h>
@@ -50,6 +52,8 @@ run(struct module_run_context *ctx)
 {
     const struct bar *bar = ctx->module->bar;
 
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
+
     while (true) {
         time_t now = time(NULL);
         time_t now_no_secs = now / 60 * 60;
diff --git a/modules/i3/i3.c b/modules/i3/i3.c
index c9cff0c..11e9caf 100644
--- a/modules/i3/i3.c
+++ b/modules/i3/i3.c
@@ -287,6 +287,8 @@ run(struct module_run_context *ctx)
     send_pkg(sock, I3_IPC_MESSAGE_TYPE_GET_WORKSPACES, NULL);
     send_pkg(sock, I3_IPC_MESSAGE_TYPE_SUBSCRIBE, "[\"workspace\"]");
 
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
+
     char buf[1 * 1024 * 1024];  /* Some replies are *big*. TODO: grow dynamically */
     size_t buf_idx = 0;
 
diff --git a/modules/label/label.c b/modules/label/label.c
index c215380..4e6c2dc 100644
--- a/modules/label/label.c
+++ b/modules/label/label.c
@@ -1,6 +1,8 @@
 #include "label.h"
 
 #include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
 #include <assert.h>
 
 #include <poll.h>
@@ -28,6 +30,7 @@ content(struct module *mod)
 static int
 run(struct module_run_context *ctx)
 {
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
     return 0;
 }
 
diff --git a/modules/xkb/xkb.c b/modules/xkb/xkb.c
index 1087e48..6e70b98 100644
--- a/modules/xkb/xkb.c
+++ b/modules/xkb/xkb.c
@@ -2,6 +2,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <assert.h>
 #include <errno.h>
 
@@ -437,6 +438,9 @@ run(struct module_run_context *ctx)
         return EXIT_FAILURE;
     }
 
+    /* TODO: move this to later */
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
+
     int ret = talk_to_xkb(ctx->abort_fd, ctx->module->bar, ctx->module->private, conn)
         ? EXIT_SUCCESS : EXIT_FAILURE;
 
diff --git a/modules/xwindow/xwindow.c b/modules/xwindow/xwindow.c
index 5779e14..7200869 100644
--- a/modules/xwindow/xwindow.c
+++ b/modules/xwindow/xwindow.c
@@ -207,6 +207,8 @@ run(struct module_run_context *ctx)
     update_title(m);
     mod->bar->refresh(mod->bar);
 
+    write(ctx->ready_fd, &(uint64_t){1}, sizeof(uint64_t));
+
     int xcb_fd = xcb_get_file_descriptor(m->conn);
     while (true) {
         struct pollfd fds[] = {{.fd = ctx->abort_fd, .events = POLLIN},