diff --git a/R/later.R b/R/later.R
index 886c240e..ffa15095 100644
--- a/R/later.R
+++ b/R/later.R
@@ -104,7 +104,7 @@ create_loop <- function(parent = current_loop(), autorun = NULL) {
   lockBinding("id", loop)
 
   # Add a weak reference to the loop object in our registry.
-  .loops[[sprintf("%d", id)]] <- new_weakref(loop)
+  .loops[[as.character(id)]] <- new_weakref(loop)
 
   if (id != 0L) {
     # Inform the C++ layer that there are no more R references when the handle
@@ -126,7 +126,7 @@ notify_r_ref_deleted <- function(loop) {
 
   res <- notifyRRefDeleted(loop$id)
   if (res) {
-    rm(list = sprintf("%d", loop$id), envir = .loops)
+    rm(list = as.character(loop$id), envir = .loops)
   }
   invisible(res)
 }
@@ -140,7 +140,7 @@ destroy_loop <- function(loop) {
 
   res <- deleteCallbackRegistry(loop$id)
   if (res) {
-    rm(list = sprintf("%d", loop$id), envir = .loops)
+    rm(list = as.character(loop$id), envir = .loops)
   }
   invisible(res)
 }
@@ -155,7 +155,7 @@ exists_loop <- function(loop) {
 #' @export
 current_loop <- function() {
   id <- getCurrentRegistryId()
-  loop_weakref <- .loops[[sprintf("%d", id)]]
+  loop_weakref <- .loops[[as.character(id)]]
   if (is.null(loop_weakref)) {
     stop("Current loop with id ", id, " not found.")
   }
diff --git a/inst/include/later.h b/inst/include/later.h
index f935e048..f767e152 100644
--- a/inst/include/later.h
+++ b/inst/include/later.h
@@ -141,7 +141,7 @@ class BackgroundTask {
     pthread_attr_init(&attr);
     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
     pthread_t t;
-    pthread_create(&t, NULL, BackgroundTask::task_main, this);
+    pthread_create(&t, &attr, BackgroundTask::task_main, this);
     pthread_attr_destroy(&attr);
 #else
     HANDLE hThread = ::CreateThread(
diff --git a/src/Makevars.in b/src/Makevars.in
index f466648c..f7be559a 100644
--- a/src/Makevars.in
+++ b/src/Makevars.in
@@ -1,4 +1,4 @@
-PKG_CPPFLAGS = -pthread -DSTRICT_R_HEADERS @pkg_cppflags@
+PKG_CPPFLAGS = -pthread -DSTRICT_R_HEADERS -DRCPP_NO_MODULES @pkg_cppflags@
 PKG_LIBS = -pthread @extra_pkg_libs@
 
 #### Debugging flags ####
diff --git a/src/Makevars.win b/src/Makevars.win
index c0ecc8ae..869cd320 100644
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -1,4 +1,4 @@
-PKG_CPPFLAGS = -DSTRICT_R_HEADERS
+PKG_CPPFLAGS = -DSTRICT_R_HEADERS -DRCPP_NO_MODULES
 PKG_LIBS = -lWs2_32
 
 #### Debugging flags ####
diff --git a/src/later_posix.cpp b/src/later_posix.cpp
index dae77c0d..2741ef3a 100644
--- a/src/later_posix.cpp
+++ b/src/later_posix.cpp
@@ -55,9 +55,7 @@ void set_fd(bool ready) {
       hot = true;
     } else {
       if (read(pipe_out, buf, BUF_SIZE) < 0) {
-        // TODO: This sets a warning but it doesn't get displayed until
-        // after the next R command is executed. Can we make it sooner?
-        Rf_warning("Failed to read out of pipe for later package");
+        Rf_warningcall_immediate(R_NilValue, "Failed to read out of pipe for later package");
       }
       hot = false;
     }