diff --git a/e6502.c b/e6502.c
index 4921282..3ce93b2 100644
--- a/e6502.c
+++ b/e6502.c
@@ -933,8 +933,8 @@ int e6502_run(e6502_Core* core,
               int instructions) {
     int status = 0;
     int i_count = 0;
-    int start = (instructions ? i_count : core->cycle);
-    int end = start + remaining;
+    uint64_t start = (instructions ? i_count : core->cycle);
+    uint64_t end = start + remaining;
     int last_pc = -1;
     while ((instructions ? i_count : core->cycle) < end) {
 #ifdef E6502_HCF
diff --git a/e6502.h b/e6502.h
index 99787a8..ab865b7 100644
--- a/e6502.h
+++ b/e6502.h
@@ -45,7 +45,7 @@ typedef struct {
     e6502_Write* bus_write;
     void*        bus_context;
 #endif
-    int cycle;
+    uint64_t cycle;
 } e6502_Core;
 
 #define e6502_Memory_Stack  (0x0100U)