diff --git a/crates/bevy_time/src/fixed_timestep.rs b/crates/bevy_time/src/fixed_timestep.rs
index eaf2eb675d..f8df270565 100644
--- a/crates/bevy_time/src/fixed_timestep.rs
+++ b/crates/bevy_time/src/fixed_timestep.rs
@@ -65,7 +65,8 @@ impl FixedTime {
 
     /// Expends one `period` of accumulated time.
     ///
-    /// [`Err(FixedUpdateError`)] will be returned
+    /// [`Err(FixedUpdateError`)] will be returned if there is
+    /// not enough accumulated time to span an entire period.
     pub fn expend(&mut self) -> Result<(), FixedUpdateError> {
         if let Some(new_value) = self.accumulated.checked_sub(self.period) {
             self.accumulated = new_value;