diff --git a/src/nese.c b/src/nese.c
index 0b09a9b..ec7fd42 100644
--- a/src/nese.c
+++ b/src/nese.c
@@ -1,3 +1,4 @@
+#include <inttypes.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <time.h>
@@ -42,10 +43,16 @@ static nes sys = {0};
 int main(int argc, char* argv[]) {
     int status = 0;
 
-    int n_loops = (argc > 1) ? atoi(argv[1]) : 0;
-    if (n_loops <= 0) n_loops = INT_MAX;
+    FILE* cart_file = stdin;
+    if (argc > 1) cart_file = fopen(argv[1], "rb");
+    if (NULL == cart_file) {
+        status = -1;
+        fprintf(stderr, "Could not open %s\n", argv[1]);
+    }
 
-    status = nes_cart_init_file(&sys.cart, stdin);
+    if (status == 0) {
+        status = nes_cart_init_file(&sys.cart, cart_file);
+    }
 
     nes_Renderer* rend = &sdl_renderer;
     if (status == 0) {
@@ -76,7 +83,7 @@ int main(int argc, char* argv[]) {
         uint64_t cycle_last_frame = 0;
 
         uint64_t total_cycles = 0;
-        for (int i = 0; i < n_loops && status == 0; ++i) {
+        for (int i = 0; status == 0; ++i) {
             int run = 0;
             nes_ppu_Result result = nes_step(&sys, &run);
             total_cycles += run;
@@ -122,7 +129,7 @@ int main(int argc, char* argv[]) {
         float ms_run = (    total_cycles * 1000. *
                             nes_clock_master_den) /
                        nes_clock_master_num;
-        fprintf(stdout, "Ran %f ms, %lu master cycles (%s)\n",
+        fprintf(stdout, "Ran %f ms, %"PRIu64" master cycles (%s)\n",
                         ms_run, total_cycles,
                         status == 0 ? "OK" : "Halted");
     }