diff --git a/board/safety.h b/board/safety.h
index 82e611f4a5..758223fbfc 100644
--- a/board/safety.h
+++ b/board/safety.h
@@ -505,9 +505,7 @@ float interpolate(struct lookup_t xy, float x) {
         float dx = xy.x[i+1] - x0;
         float dy = xy.y[i+1] - y0;
         // dx should not be zero as xy.x is supposed to be monotonic
-        if (dx <= 0.) {
-          dx = 0.0001;
-        }
+        dx = MAX(dx, 0.0001);
         ret = (dy * (x - x0) / dx) + y0;
         break;
       }
diff --git a/tests/safety/common.py b/tests/safety/common.py
index f9b62e8992..701753bfcb 100644
--- a/tests/safety/common.py
+++ b/tests/safety/common.py
@@ -1046,3 +1046,10 @@ def test_vehicle_moving(self):
     # past threshold
     self._rx(self._vehicle_moving_msg(self.STANDSTILL_THRESHOLD + 1))
     self.assertTrue(self.safety.get_vehicle_moving())
+
+  def test_safety_tick(self):
+    self.safety.set_timer(int(2e6))
+    self.safety.set_controls_allowed(True)
+    self.safety.safety_tick_current_safety_config()
+    self.assertFalse(self.safety.get_controls_allowed())
+    self.assertFalse(self.safety.safety_config_valid())
diff --git a/tests/safety/test_coverage.sh b/tests/safety/test_coverage.sh
index c5168004ae..a1dc1f046f 100755
--- a/tests/safety/test_coverage.sh
+++ b/tests/safety/test_coverage.sh
@@ -17,7 +17,7 @@ fi
 
 # test coverage
 GCOV_OUTPUT=$(gcov -n ../libpanda/panda.c)
-INCOMPLETE_COVERAGE=$(echo "$GCOV_OUTPUT" | paste -s -d' \n' | grep "File.*safety/safety_.*.h" | grep -v "100.00%" || true)
+INCOMPLETE_COVERAGE=$(echo "$GCOV_OUTPUT" | paste -s -d' \n' | grep -E "File.*(safety\/safety_.*)|(safety)\.h" | grep -v "100.00%" || true)
 if [ -n "$INCOMPLETE_COVERAGE" ]; then
   echo "FAILED: Some files have less than 100% coverage:"
   echo "$INCOMPLETE_COVERAGE"