diff --git a/Cargo.toml b/Cargo.toml
index ed8ad55..96ab8a9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,5 +13,8 @@ readme = "readme.md"
 categories = ["command-line-interface"]
 keywords = ["ascii", "table"]
 
+[dependencies]
+regex = "1"
+
 [dev-dependencies]
 colorful = "0.2"
diff --git a/src/lib.rs b/src/lib.rs
index 1e10fc2..c5da011 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -225,14 +225,14 @@ impl AsciiTable {
         let result: Vec<_> = (0..num_cols).map(|a| {
             let default_conf = &DEFAULT_COLUMN;
             let conf = self.columns.get(&a).unwrap_or(default_conf);
-            let column_width = data.iter().map(|row| Self::count_characters(&row[a])).max().unwrap();
+            let column_width = data.iter().map(|row| self.count_characters(&row[a])).max().unwrap();
             let header_width = conf.header.chars().count();
             column_width.max(header_width).min(conf.max_width)
         }).collect();
         self.truncate_widths(result)
     }
 
-    fn count_characters(cell: &str) -> usize {
+    fn count_characters(&self, cell: &str) -> usize {
         cell.chars().count()
     }