diff --git a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-2.c b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-2.c
index a66aef4cf9..4825ff6f22 100644
--- a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-2.c
+++ b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-2.c
@@ -72,6 +72,8 @@ void *t1_func(void *arg)
 		fprintf(stderr,"Test FAILED: pthread_cond_timedwait return %d instead of ETIMEDOUT\n", rc);
 		pthread_exit((void*)PTS_FAIL);
         }
+
+	return NULL;
 }
 
 int main()
diff --git a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-3.c b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-3.c
index a2380f2c08..f887f6d0d0 100644
--- a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-3.c
+++ b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_cond_timedwait/2-3.c
@@ -62,6 +62,8 @@ void *t1_func(void *arg)
 		fprintf(stderr,"pthread_cond_timedwait return %d instead of ETIMEDOUT\n", rc);
 		exit(PTS_FAIL);
         }
+
+	return NULL;
 }
 
 int main()
diff --git a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/1-2.c b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/1-2.c
index ccf56a4c49..42c888bdce 100644
--- a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/1-2.c
+++ b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/1-2.c
@@ -41,6 +41,7 @@ void *a_thread_func()
 	}
 
 	pthread_exit(0);
+	return NULL;
 }
 
 int main()
diff --git a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/3-1.c b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/3-1.c
index 56cb1f8cae..fae1cc3f12 100644
--- a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/3-1.c
+++ b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_key_create/3-1.c
@@ -50,6 +50,7 @@ void *a_thread_func()
 	
 	/* The thread ends here, the destructor for the key should now be called after this */
 	pthread_exit(0);
+	return NULL;
 }
 
 int main()
diff --git a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_mutexattr_settype/3-2.c b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_mutexattr_settype/3-2.c
index c75db31404..a2c421b502 100644
--- a/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_mutexattr_settype/3-2.c
+++ b/src/tests/system/libroot/posix/posixtestsuite/conformance/interfaces/pthread_mutexattr_settype/3-2.c
@@ -42,6 +42,7 @@ void *a_thread_func()
 	/* Try to unlock the mutex that main already locked. */
 	ret=pthread_mutex_unlock(&mutex);
 	pthread_exit((void*)0);
+	return NULL;
 }