diff --git a/R/pool.r b/R/pool.r
index 06d72fc..2a0284e 100644
--- a/R/pool.r
+++ b/R/pool.r
@@ -34,6 +34,7 @@ Pool = R6::R6Class("Pool",
 
         add = function(qsys, n, ...) {
             self$workers = qsys$new(addr=private$addr, master=private$master, n_jobs=n, ...)
+            private$master$add_pending_workers(n)
         },
 
         env = function(...) {
@@ -127,7 +128,10 @@ Pool = R6::R6Class("Pool",
     ),
 
     active = list(
-        workers_total = function() self$workers$n(),
+        workers_total = function() {
+            ls_w = private$master$list_workers()
+            length(ls_w$worker) + ls_w$pending
+        },
         workers_running = function() length(private$master$list_workers()$worker),
         reusable = function() private$reuse
     ),
diff --git a/src/CMQMaster.cpp b/src/CMQMaster.cpp
index cea68d9..72ff2b9 100644
--- a/src/CMQMaster.cpp
+++ b/src/CMQMaster.cpp
@@ -15,6 +15,7 @@ RCPP_MODULE(cmq_master) {
         .method("add_env", &CMQMaster::add_env)
         .method("add_pkg", &CMQMaster::add_pkg)
         .method("list_env", &CMQMaster::list_env)
+        .method("add_pending_workers", &CMQMaster::add_pending_workers)
         .method("list_workers", &CMQMaster::list_workers)
     ;
 }
diff --git a/src/CMQMaster.h b/src/CMQMaster.h
index 7bd14f7..e47914d 100644
--- a/src/CMQMaster.h
+++ b/src/CMQMaster.h
@@ -44,8 +44,8 @@ class CMQMaster {
     }
 
     SEXP recv(int timeout=-1) {
-//        if (peers.size() == 0)
-//            Rf_error("Trying to receive data without workers");
+        if (peers.size() + pending_workers <= 0)
+            Rf_error("Trying to receive data without workers");
 
         int data_offset;
         std::vector<zmq::message_t> msgs;
@@ -156,6 +156,10 @@ class CMQMaster {
                 Rcpp::_["size"] = Rcpp::wrap(sizes));
     }
 
+    void add_pending_workers(int n) {
+        pending_workers += n;
+    }
+
     Rcpp::List list_workers() {
         std::vector<std::string> names;
         names.reserve(peers.size());
@@ -172,7 +176,8 @@ class CMQMaster {
             Rcpp::_["worker"] = Rcpp::wrap(names),
             Rcpp::_["status"] = Rcpp::wrap(status),
             Rcpp::_["time"] = wtime,
-            Rcpp::_["mem"] = mem
+            Rcpp::_["mem"] = mem,
+            Rcpp::_["pending"] = pending_workers
         );
     }
 
@@ -188,6 +193,7 @@ class CMQMaster {
 
     zmq::context_t *ctx {nullptr};
     int has_proxy {0};
+    int pending_workers {0};
     zmq::socket_t sock;
     std::string cur;
     std::unordered_map<std::string, worker_t> peers;
@@ -238,7 +244,9 @@ class CMQMaster {
             ++cur_i;
 
         cur = msgs[cur_i].to_string();
+        int prev_size = peers.size();
         auto &w = peers[cur];
+        pending_workers -= peers.size() - prev_size;
         w.call = R_NilValue;
         if (cur_i == 1)
             w.via = msgs[0].to_string();
diff --git a/tests/testthat/test-2-worker.r b/tests/testthat/test-2-worker.r
index 2f425b7..081239a 100644
--- a/tests/testthat/test-2-worker.r
+++ b/tests/testthat/test-2-worker.r
@@ -3,6 +3,7 @@ context("worker usage")
 test_that("timeouts are triggered correctly", {
     m = methods::new(CMQMaster)
     addr = m$listen("inproc://endpoint")
+    m$add_pending_workers(1L)
     expect_error(m$recv(0L))
     m$close(0L)
 
@@ -15,6 +16,7 @@ test_that("worker evaluation", {
     m = methods::new(CMQMaster)
     w = methods::new(CMQWorker, m$context())
     addr = m$listen("inproc://endpoint")
+    m$add_pending_workers(1L)
     w$connect(addr, 0L)
 
     m$recv(0L)
@@ -33,6 +35,7 @@ test_that("export variable to worker", {
     m = methods::new(CMQMaster)
     w = methods::new(CMQWorker, m$context())
     addr = m$listen("inproc://endpoint")
+    m$add_pending_workers(1L)
     w$connect(addr, 0L)
 
     m$add_env("x", 3)
@@ -58,6 +61,7 @@ test_that("load package on worker", {
     m = methods::new(CMQMaster)
     w = methods::new(CMQWorker, m$context())
     addr = m$listen("inproc://endpoint")
+    m$add_pending_workers(1L)
     w$connect(addr, 0L)
 
     m$add_pkg("parallel")
@@ -80,6 +84,7 @@ test_that("errors are sent back to master", {
     m = methods::new(CMQMaster)
     w = methods::new(CMQWorker, m$context())
     addr = m$listen("inproc://endpoint")
+    m$add_pending_workers(1L)
     w$connect(addr, 0L)
 
     m$recv(0L)
@@ -100,6 +105,7 @@ test_that("worker R API", {
 
     m = methods::new(CMQMaster)
     addr = m$listen("tcp://127.0.0.1:*")
+    m$add_pending_workers(1L)
 #    addr = m$listen("inproc://endpoint") # mailbox.cpp assertion error
 
     p = parallel::mcparallel(worker(addr))
@@ -120,6 +126,7 @@ test_that("communication with two workers", {
 
     m = methods::new(CMQMaster)
     addr = m$listen("tcp://127.0.0.1:*")
+    m$add_pending_workers(2L)
     w1 = parallel::mcparallel(worker(addr))
     w2 = parallel::mcparallel(worker(addr))