diff --git a/c_src/async_nif.h b/c_src/async_nif.h
index d25b35f..4938ed0 100644
--- a/c_src/async_nif.h
+++ b/c_src/async_nif.h
@@ -96,7 +96,7 @@ struct async_nif_state {
     new_env = req->env;                                                 \
     if (!req)                                                           \
       return enif_make_tuple2(env, enif_make_atom(env, "error"),        \
-                              enif_make_atom(env, "enomem"));           \
+                              enif_make_atom(env, "eagain"));           \
     do pre_block while(0);                                              \
     copy_of_args = (struct decl ## _args *)enif_alloc(sizeof(struct decl ## _args)); \
     if (!copy_of_args) {                                                \
diff --git a/src/async_nif.hrl b/src/async_nif.hrl
index 5110fa2..9d0f215 100644
--- a/src/async_nif.hrl
+++ b/src/async_nif.hrl
@@ -21,22 +21,25 @@
 %%
 %% -------------------------------------------------------------------
 
--define(ASYNC_NIF_CALL(Fun, Args),
-        begin
-            NIFRef = erlang:make_ref(),
-            case erlang:apply(Fun, [NIFRef|Args]) of
-                {ok, enqueued} ->
-                    receive
-                        {NIFRef, {error, shutdown}=Error} ->
-                            %% Work unit was queued, but not executed.
-                            Error;
-                        {NIFRef, {error, _Reason}=Error} ->
-                            %% Work unit returned an error.
-                            Error;
-                        {NIFRef, Reply} ->
-                            Reply
-                    end;
-                Other ->
-                    Other
-            end
-        end).
+-spec async_nif_enqueue(reference(), function(), [term()]) -> term() | {error, term()}.
+async_nif_enqueue(R, F, A) ->
+    case erlang:apply(F, [R|A]) of
+        {ok, enqueued} ->
+            receive
+                {R, {error, eagain}} ->
+                    %% Work unit was not queued, try again.
+                    async_nif_enqueue(R, F, A);
+                {R, {error, shutdown}=Error} ->
+                    %% Work unit was queued, but not executed.
+                    Error;
+                {R, {error, _Reason}=Error} ->
+                    %% Work unit returned an error.
+                    Error;
+                {R, Reply} ->
+                    Reply
+            end;
+        Other ->
+            Other
+    end.
+
+-define(ASYNC_NIF_CALL(Fun, Args), async_nif_enqueue(erlang:make_ref(), Fun, Args)).
diff --git a/src/wterl.erl b/src/wterl.erl
index 1b3c3d7..1e8c8bf 100644
--- a/src/wterl.erl
+++ b/src/wterl.erl
@@ -69,8 +69,6 @@
 
 -export([set_event_handler_pid/1]).
 
--include("async_nif.hrl").
-
 -ifdef(TEST).
 -ifdef(EQC).
 -include_lib("eqc/include/eqc.hrl").
@@ -90,6 +88,7 @@
 
 -on_load(init/0).
 
+-include("async_nif.hrl").
 -define(nif_stub, nif_stub_error(?LINE)).
 nif_stub_error(Line) ->
     erlang:nif_error({nif_not_loaded,module,?MODULE,line,Line}).