diff --git a/c/src/tests/psxtests/psx05/init.c b/c/src/tests/psxtests/psx05/init.c
index 71340da59e..a6f25fd42b 100644
--- a/c/src/tests/psxtests/psx05/init.c
+++ b/c/src/tests/psxtests/psx05/init.c
@@ -96,6 +96,10 @@ void *POSIX_Init(
   
   /* basic checkout of mutex attributes */
 
+  puts( "Init: pthread_mutexattr_init - EINVAL (NULL attr)" );
+  status = pthread_mutexattr_init( NULL );
+  assert( status == EINVAL );
+
   puts( "Init: pthread_mutexattr_init - SUCCESSFUL" );
   status = pthread_mutexattr_init( &attr );
   assert( !status );
diff --git a/testsuites/psxtests/psx05/init.c b/testsuites/psxtests/psx05/init.c
index 71340da59e..a6f25fd42b 100644
--- a/testsuites/psxtests/psx05/init.c
+++ b/testsuites/psxtests/psx05/init.c
@@ -96,6 +96,10 @@ void *POSIX_Init(
   
   /* basic checkout of mutex attributes */
 
+  puts( "Init: pthread_mutexattr_init - EINVAL (NULL attr)" );
+  status = pthread_mutexattr_init( NULL );
+  assert( status == EINVAL );
+
   puts( "Init: pthread_mutexattr_init - SUCCESSFUL" );
   status = pthread_mutexattr_init( &attr );
   assert( !status );