diff --git a/src/timer.rs b/src/timer.rs
line changes: +2/-4
index d682d0b..8e552e1
--- a/src/timer.rs
+++ b/src/timer.rs

@@ -67,7 +67,7 @@ impl Timer {
                 (None, None) => Ordering::Equal,
             }
         });
-        if let Some(tc) = self.callbacks[0] {
+        if let Some(_) = self.callbacks[0] {
             self.systick.start(1 as Ms);
         } else {
             self.systick.stop();

@@ -85,9 +85,7 @@ impl Timer {
             };
             if timer_expired {
                 let tc = self.callbacks[0].take().unwrap();
-                unsafe {
-                    (tc.f)();
-                }
+                (tc.f)();
                 self.recalculate();
             }
         }