diff --git a/src/font/sprite/underline.zig b/src/font/sprite/underline.zig
index 67bc38b41..3a7d5cb98 100644
--- a/src/font/sprite/underline.zig
+++ b/src/font/sprite/underline.zig
@@ -163,7 +163,9 @@ fn drawDashed(alloc: Allocator, width: u32, thickness: u32) !CanvasAndOffset {
 /// geometry.
 fn drawCurly(alloc: Allocator, width: u32, thickness: u32) !CanvasAndOffset {
     const float_width: f64 = @floatFromInt(width);
-    const float_thick: f64 = @floatFromInt(thickness);
+    // Because of we way we draw the undercurl, we end up making it around 1px
+    // thicker than it should be, to fix this we just reduce the thickness by 1.
+    const float_thick: f64 = @floatFromInt(@max(1, thickness -| 1));
 
     // Calculate the wave period for a single character
     //   `2 * pi...` = 1 peak per character