diff --git a/src/modules/api/libapi.c b/src/modules/api/libapi.c
index 1a10b6b7cf17..9176e9c59655 100644
--- a/src/modules/api/libapi.c
+++ b/src/modules/api/libapi.c
@@ -45,14 +45,19 @@
 #include "src/common/libutil/xzmalloc.h"
 #include "src/common/libutil/zfd.h"
 
+/* deferred message queue */
+typedef struct {
+    zlist_t *resp;
+    zlist_t *event;
+} dq_t;
+
 
 #define CMB_CTX_MAGIC   0xf434aaab
 typedef struct {
     int magic;
     int fd;
     int rank;
-    zlist_t *resp;      /* deferred */
-    zlist_t *event;     /* deferred */
+    dq_t *dq;
     flux_t h;
     zloop_t *zloop;
     bool reactor_stop;
@@ -73,31 +78,67 @@ static int cmb_request_sendmsg (void *impl, zmsg_t **zmsg)
     return zfd_send_typemask (c->fd, FLUX_MSGTYPE_REQUEST, zmsg);
 }
 
-static void append_deferred (cmb_t *c, zmsg_t **zmsg, int typemask)
+static dq_t *dq_create (void)
+{
+    dq_t *dq = xzmalloc (sizeof (*dq));
+    if (!(dq->resp = zlist_new ()))
+        oom ();
+    if (!(dq->event = zlist_new ()))
+        oom ();
+    return dq;
+}
+
+static void dq_destroy (dq_t *dq)
+{
+    zmsg_t *z;
+    while ((z = zlist_pop (dq->resp)))
+        zmsg_destroy (&z);
+    zlist_destroy (&dq->resp);
+    while ((z = zlist_pop (dq->event)))
+        zmsg_destroy (&z);
+    zlist_destroy (&dq->event);
+    free (dq);
+}
+
+static int dq_put (dq_t *dq, zmsg_t **zmsg, int typemask)
 {
     if ((typemask & FLUX_MSGTYPE_EVENT)) {
-        if (zlist_append (c->event, *zmsg) < 0)
-            oom ();
+        if (zlist_append (dq->event, *zmsg) < 0)
+            return -1;
     } else if ((typemask & FLUX_MSGTYPE_RESPONSE)) {
-        if (zlist_append (c->resp, *zmsg) < 0)
-            oom ();
+        if (zlist_append (dq->resp, *zmsg) < 0)
+            return -1;
     } else {
         zmsg_destroy (zmsg);
     }
     *zmsg = NULL;
+    return 0;
+}
+
+static bool dq_get (dq_t *dq, zmsg_t **zmsg, int typemask)
+{
+    zmsg_t *z = NULL;
+    if ((typemask & FLUX_MSGTYPE_EVENT)) {
+        z = zlist_pop (dq->event);
+    } else if ((typemask & FLUX_MSGTYPE_RESPONSE)) {
+        z = zlist_pop (dq->resp);
+    }
+    if (z)
+        *zmsg = z;
+    return (z != NULL);
 }
 
 static int process_deferred (cmb_t *c)
 {
     zmsg_t *zmsg;
 
-    while ((zmsg = zlist_pop (c->event))) {
+    while ((dq_get (c->dq, &zmsg, FLUX_MSGTYPE_EVENT))) {
         if (flux_handle_event_msg (c->h, FLUX_MSGTYPE_EVENT, &zmsg) < 0) {
             cmb_reactor_stop (c, -1);
             goto done;
         }
     }
-    while ((zmsg = zlist_pop (c->resp))) {
+    while ((dq_get (c->dq, &zmsg, FLUX_MSGTYPE_RESPONSE))) {
         if (flux_handle_event_msg (c->h, FLUX_MSGTYPE_RESPONSE, &zmsg) < 0) {
             cmb_reactor_stop (c, -1);
             goto done;
@@ -114,10 +155,11 @@ static zmsg_t *cmb_response_recvmsg (void *impl, bool nonblock)
     int typemask;
 
     assert (c->magic == CMB_CTX_MAGIC);
-    if (!(z = zlist_pop (c->resp))) {
-        while ((z = zfd_recv_typemask (c->fd, &typemask, nonblock)) 
+    if (!dq_get (c->dq, &z, FLUX_MSGTYPE_RESPONSE)) {
+        while ((z = zfd_recv_typemask (c->fd, &typemask, nonblock))
                                         && !(typemask & FLUX_MSGTYPE_RESPONSE))
-            append_deferred (c, &z, typemask);
+            if (dq_put (c->dq, &z, typemask) < 0)
+                oom ();
     }
     return z;
 }
@@ -126,10 +168,7 @@ static int cmb_response_putmsg (void *impl, zmsg_t **zmsg)
 {
     cmb_t *c = impl;
     assert (c->magic == CMB_CTX_MAGIC);
-    if (zlist_append (c->resp, *zmsg) < 0)
-        return -1;
-    *zmsg = NULL;
-    return 0;
+    return dq_put (c->dq, zmsg, FLUX_MSGTYPE_RESPONSE);
 }
 
 static int cmb_event_subscribe (void *impl, const char *s)
@@ -153,10 +192,10 @@ static zmsg_t *cmb_event_recvmsg (void *impl, bool nonblock)
     int typemask;
 
     assert (c->magic == CMB_CTX_MAGIC);
-    if (!(z = zlist_pop (c->event))) {
+    if (!dq_get (c->dq, &z, FLUX_MSGTYPE_EVENT)) {
         while ((z = zfd_recv_typemask (c->fd, &typemask, nonblock))
                                         && !(typemask & FLUX_MSGTYPE_EVENT))
-            append_deferred (c, &z, typemask);
+            dq_put (c->dq, &z, typemask);
     }
     return z;
 }
@@ -300,19 +339,13 @@ static void cmb_reactor_tmout_remove (void *impl, int timer_id)
 static void cmb_fini (void *impl)
 {
     cmb_t *c = impl;
-    zmsg_t *z;
 
     assert (c->magic == CMB_CTX_MAGIC);
     if (c->fd >= 0)
         (void)close (c->fd);
     if (c->zloop)
         zloop_destroy (&c->zloop);
-    while ((z = zlist_pop (c->resp)))
-        zmsg_destroy (&z);
-    zlist_destroy (&c->resp);
-    while ((z = zlist_pop (c->event)))
-        zmsg_destroy (&z);
-    zlist_destroy (&c->event);
+    dq_destroy (c->dq);
     free (c);
 }
 
@@ -342,11 +375,8 @@ flux_t flux_api_openpath (const char *path, int flags)
     char *pidfile = NULL;
 
     c = xzmalloc (sizeof (*c));
-    if (!(c->resp = zlist_new ()))
-        oom ();
-    if (!(c->event = zlist_new ()))
-        oom ();
     c->magic = CMB_CTX_MAGIC;
+    c->dq = dq_create ();
     c->rank = -1;
     if (!(c->zloop = zloop_new ()))
         oom ();