diff --git a/src/utils/mod.rs b/src/utils/mod.rs
index 04cec20..a4f9bcf 100644
--- a/src/utils/mod.rs
+++ b/src/utils/mod.rs
@@ -48,12 +48,15 @@ pub fn prefix<'a, I>(iter: I, available_width: usize, delimiter: &str) -> Prefix
     let delimiter_width = delimiter.width();
     let delimiter_len = delimiter.len();
 
+    // `current_width` is the width of everything
+    // before the next token, including any space.
     let mut current_width = 0;
     let sum = iter.take_while(|token| {
             let width = token.width();
             if current_width + width > available_width {
                 false
             } else {
+                // Include the delimiter after this token.
                 current_width += width;
                 current_width += delimiter_width;
                 true
@@ -66,6 +69,7 @@ pub fn prefix<'a, I>(iter: I, available_width: usize, delimiter: &str) -> Prefix
     // but only if the iterator was non empty.
     let length = sum.saturating_sub(delimiter_len);
 
+    // `current_width` includes a delimiter after the last token
     debug_assert!(current_width <= available_width + delimiter_width);
 
     Prefix {