diff --git a/base_c/src/thread.c b/base_c/src/thread.c
index 01240db..dc26db5 100644
--- a/base_c/src/thread.c
+++ b/base_c/src/thread.c
@@ -80,7 +80,7 @@ void embb_thread_yield() {
 
 int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
                        embb_thread_start_t func, void *arg) {
-  assert(thread != NULL);
+  if (thread == NULL) return EMBB_ERROR;
   thread->embb_internal_arg = (embb_internal_thread_arg_t*)
                               embb_alloc(sizeof(embb_internal_thread_arg_t));
   if (thread->embb_internal_arg == NULL) {
@@ -98,6 +98,8 @@ int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
       0,                                  /* no creation arguments */
       0);                                 /* no system thread ID */
   if (thread->embb_internal_handle == NULL) {
+    embb_free(thread->embb_internal_arg);
+    thread->embb_internal_arg = NULL;
     return EMBB_ERROR;
   }
 
@@ -121,6 +123,7 @@ int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
 }
 
 int embb_thread_join(embb_thread_t* thread, int* result_code) {
+  if (thread == NULL) return EMBB_ERROR;
   BOOL success;
   DWORD result;
   result = WaitForSingleObject(thread->embb_internal_handle, INFINITE);
@@ -206,6 +209,7 @@ void embb_thread_yield() {
 
 int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
                        embb_thread_start_t func, void* arg) {
+  if (thread == NULL) return EMBB_ERROR;
   pthread_attr_t attr; /* Used to set thread affinities */
   int status = pthread_attr_init(&attr);
   if (status != 0) return EMBB_ERROR;
@@ -226,7 +230,11 @@ int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
       }
     }
     status = pthread_attr_setaffinity_np(&attr, sizeof(cpuset), &cpuset);
-    if (status != 0) return EMBB_ERROR;
+    if (status != 0) {
+      thread->embb_internal_arg = NULL;
+      thread->embb_internal_handle = NULL;
+      return EMBB_ERROR;
+    }
 #else
     embb_log_write("base_c", EMBB_LOG_LEVEL_WARNING, "Could not set thread "
                    "affinity, since no implementation available!\n");
@@ -259,11 +267,14 @@ int embb_thread_create(embb_thread_t* thread, const embb_core_set_t* core_set,
 
 int embb_thread_join(embb_thread_t* thread, int *result_code) {
   int status = 0;
+  if (thread == NULL) return EMBB_ERROR;
   status = pthread_join(thread->embb_internal_handle, NULL);
-  if (result_code != NULL) {
-    *result_code = thread->embb_internal_arg->result;
+  if (thread->embb_internal_arg != NULL) {
+    if (result_code != NULL) {
+      *result_code = thread->embb_internal_arg->result;
+    }
+    embb_free(thread->embb_internal_arg);
   }
-  embb_free(thread->embb_internal_arg);
   if (status != 0) {
     return EMBB_ERROR;
   }