diff --git a/aw_watcher_afk/windows.py b/aw_watcher_afk/windows.py
index a55f7cb..675e3e7 100644
--- a/aw_watcher_afk/windows.py
+++ b/aw_watcher_afk/windows.py
@@ -1,8 +1,10 @@
 import ctypes
 import time
-from ctypes import POINTER, WINFUNCTYPE, Structure  # type: ignore
+from ctypes import POINTER, WINFUNCTYPE, Structure, c_ulonglong  # type: ignore
 from ctypes.wintypes import BOOL, DWORD, UINT
 
+ULONGLONG = c_ulonglong
+
 
 class LastInputInfo(Structure):
     _fields_ = [("cbSize", UINT), ("dwTime", DWORD)]
@@ -19,16 +21,30 @@ def _getLastInputTick() -> int:
     return lastinput.dwTime
 
 
-def _getTickCount() -> int:
-    prototype = WINFUNCTYPE(DWORD)
+def _getTickCount64() -> int:
+    """Use GetTickCount64 to avoid 32-bit overflow after ~49.7 days of uptime."""
+    prototype = WINFUNCTYPE(ULONGLONG)
     paramflags = ()
-    c_GetTickCount = prototype(("GetTickCount", ctypes.windll.kernel32), paramflags)  # type: ignore
-    return c_GetTickCount()
+    c_GetTickCount64 = prototype(("GetTickCount64", ctypes.windll.kernel32), paramflags)  # type: ignore
+    return c_GetTickCount64()
 
 
 def seconds_since_last_input():
-    seconds_since_input = (_getTickCount() - _getLastInputTick()) / 1000
-    return seconds_since_input
+    tick_count = _getTickCount64()
+    last_input_tick = _getLastInputTick()  # 32-bit DWORD from GetLastInputInfo
+
+    # GetLastInputInfo returns a 32-bit DWORD tick count that wraps at 2^32 ms.
+    # GetTickCount64 returns 64-bit. To compute the difference correctly, we
+    # compare only the lower 32 bits when the values are close (normal case),
+    # and handle the wraparound when dwTime > lower 32 bits of tick_count.
+    tick_lower32 = tick_count & 0xFFFFFFFF
+    if tick_lower32 >= last_input_tick:
+        diff_ms = tick_lower32 - last_input_tick
+    else:
+        # 32-bit wraparound: tick_count's lower bits wrapped past dwTime
+        diff_ms = (0x100000000 - last_input_tick) + tick_lower32
+
+    return diff_ms / 1000
 
 
 if __name__ == "__main__":