Segmentation fault while using -dump-error-graph

[bifbof]

Code Sample

#include <assert.h>
#include <pthread.h>

int a = 0;

void *thread(void *unused)
{
	assert(a != 0);
	return NULL;
}

int main()
{
	pthread_t t1;
	pthread_create(&t1, NULL, thread, NULL);
	return 0;
}

Problem description
If I run this with ./genmc <filename> -dump-error-graph="foo" I reach a segfault.
Accessing the global non-atomic variable in the thread is apparently causing this.