diff --git a/harness.c b/harness.c
index 0f9b691..3339c18 100644
--- a/harness.c
+++ b/harness.c
@@ -33,6 +33,7 @@ typedef unsigned char u_char;
 # error Define STACK_SIZE for your platform. It should probably not be less than 32k?
 #endif
 
+static volatile int harness_running = 1;
 Process *current_process = NULL;
 
 #define EMPTY_PROCESS_QUEUE ((queue_t) { offsetof(Process, link), 0, NULL, NULL })
@@ -234,7 +235,13 @@ void boot_harness(void) {
       //info("Polling for events\n");
       event_loop(EVLOOP_NONBLOCK);
     }
+    if (!harness_running) break;
     //info("Blocking for events\n");
     event_loop(EVLOOP_ONCE);
   }
 }
+
+void interrupt_harness(void) {
+  info("Interrupting harness\n");
+  harness_running = 0;
+}
diff --git a/harness.h b/harness.h
index 7f30309..7926e0b 100644
--- a/harness.h
+++ b/harness.h
@@ -41,5 +41,6 @@ extern int iohandle_flush(IOHandle *h);
 extern void iohandle_settimeout(IOHandle *h, int timeout_read, int timeout_write);
 
 extern void boot_harness(void);
+extern void interrupt_harness(void);
 
 #endif