diff --git a/std/os/index.zig b/std/os/index.zig
index 4f1826021f..93c5f70f1e 100644
--- a/std/os/index.zig
+++ b/std/os/index.zig
@@ -2477,6 +2477,7 @@ pub const Thread = struct {
             },
             builtin.Os.windows => {
                 assert(windows.WaitForSingleObject(self.data.handle, windows.INFINITE) == windows.WAIT_OBJECT_0);
+                assert(windows.CloseHandle(self.data.handle) != 0);
                 assert(windows.HeapFree(self.data.heap_handle, 0, self.data.alloc_start) != 0);
             },
             else => @compileError("Unsupported OS"),