diff --git a/src/alignment.rs b/src/alignment.rs
index 7284694..56bbab8 100644
--- a/src/alignment.rs
+++ b/src/alignment.rs
@@ -199,16 +199,16 @@ impl Alignment {
                 _ => {
                     x_i = self.xstart;
                     y_i = self.ystart;
-                    for k in x.iter().take(self.xstart) {
-                        x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
-                        inb_pretty.push(' ');
-                        y_pretty.push(' ')
+                    // SAFETY: validity checked before creating an Alignment
+                    unsafe {
+                        x_pretty.push_str(std::str::from_utf8_unchecked(&x[..self.xstart]));
                     }
-                    for k in y.iter().take(self.ystart) {
-                        y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
-                        inb_pretty.push(' ');
-                        x_pretty.push(' ')
+                    y_pretty.push_str(&" ".repeat(self.xstart));
+                    unsafe {
+                        y_pretty.push_str(std::str::from_utf8_unchecked(&y[..self.ystart]));
                     }
+                    x_pretty.push_str(&" ".repeat(self.ystart));
+                    inb_pretty.push_str(&" ".repeat(self.xstart + self.ystart));
                 }
             }
 
@@ -216,21 +216,21 @@ impl Alignment {
             for i in 0..self.operations.len() {
                 match self.operations[i] {
                     AlignmentOperation::Match => {
-                        x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[x[x_i]])));
+                        x_pretty.push(x[x_i] as char);
                         x_i += 1;
 
                         inb_pretty.push_str("|");
 
-                        y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[y[y_i]])));
+                        y_pretty.push(y[y_i] as char);
                         y_i += 1;
                     }
                     AlignmentOperation::Subst => {
-                        x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[x[x_i]])));
+                        x_pretty.push(x[x_i] as char);
                         x_i += 1;
 
                         inb_pretty.push('\\');
 
-                        y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[y[y_i]])));
+                        y_pretty.push(y[y_i] as char);
                         y_i += 1;
                     }
                     AlignmentOperation::Del => {
@@ -238,11 +238,11 @@ impl Alignment {
 
                         inb_pretty.push('x');
 
-                        y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[y[y_i]])));
+                        y_pretty.push(y[y_i] as char);
                         y_i += 1;
                     }
                     AlignmentOperation::Ins => {
-                        x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[x[x_i]])));
+                        x_pretty.push(x[x_i] as char);
                         x_i += 1;
 
                         inb_pretty.push('+');
@@ -251,7 +251,7 @@ impl Alignment {
                     }
                     AlignmentOperation::Xclip(len) => {
                         for k in x.iter().take(len) {
-                            x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
+                            x_pretty.push(*k as char);
                             x_i += 1;
 
                             inb_pretty.push(' ');
@@ -261,7 +261,7 @@ impl Alignment {
                     }
                     AlignmentOperation::Yclip(len) => {
                         for k in y.iter().take(len) {
-                            y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
+                            y_pretty.push(*k as char);
                             y_i += 1;
 
                             inb_pretty.push(' ');
@@ -278,12 +278,12 @@ impl Alignment {
                 AlignmentMode::Custom => {}
                 _ => {
                     for k in x.iter().take(self.xlen).skip(x_i) {
-                        x_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
+                        x_pretty.push(*k as char);
                         inb_pretty.push(' ');
                         y_pretty.push(' ')
                     }
                     for k in y.iter().take(self.ylen).skip(y_i) {
-                        y_pretty.push_str(&format!("{}", String::from_utf8_lossy(&[*k])));
+                        y_pretty.push(*k as char);
                         inb_pretty.push(' ');
                         x_pretty.push(' ')
                     }