diff --git a/mongoose.c b/mongoose.c
index f125bd52..968613be 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3494,8 +3494,10 @@ struct mg_connection *mg_wrapfd(struct mg_mgr *mgr, int fd,
 struct mg_timer *mg_timer_add(struct mg_mgr *mgr, uint64_t milliseconds,
                               unsigned flags, void (*fn)(void *), void *arg) {
   struct mg_timer *t = (struct mg_timer *) calloc(1, sizeof(*t));
-  mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
-  t->id = mgr->timerid++;
+  if (t != NULL) {
+    mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
+    t->id = mgr->timerid++;
+  }
   return t;
 }
 
diff --git a/src/net.c b/src/net.c
index eddf872c..63c830f1 100644
--- a/src/net.c
+++ b/src/net.c
@@ -224,8 +224,10 @@ struct mg_connection *mg_wrapfd(struct mg_mgr *mgr, int fd,
 struct mg_timer *mg_timer_add(struct mg_mgr *mgr, uint64_t milliseconds,
                               unsigned flags, void (*fn)(void *), void *arg) {
   struct mg_timer *t = (struct mg_timer *) calloc(1, sizeof(*t));
-  mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
-  t->id = mgr->timerid++;
+  if (t != NULL) {
+    mg_timer_init(&mgr->timers, t, milliseconds, flags, fn, arg);
+    t->id = mgr->timerid++;
+  }
   return t;
 }