diff --git a/core/sys/windows/winmm.odin b/core/sys/windows/winmm.odin
index 6d3fc409e..9edd56acc 100644
--- a/core/sys/windows/winmm.odin
+++ b/core/sys/windows/winmm.odin
@@ -6,4 +6,5 @@ foreign import winmm "system:Winmm.lib"
 @(default_calling_convention="stdcall")
 foreign winmm {
 	timeBeginPeriod :: proc(uPeriod: UINT) -> MMRESULT ---
+	timeEndPeriod :: proc(uPeriod: UINT) -> MMRESULT ---
 }