diff --git a/Cargo.toml b/Cargo.toml
index 3766102..3d6359a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "fontkit"
-version = "0.6.0-beta.7"
+version = "0.6.0-beta.8"
 edition = "2021"
 authors = ["Zimon Dai <daizhuoxian@gmail.com>"]
 description = "A simple library for font loading and indexing"
diff --git a/src/metrics.rs b/src/metrics.rs
index 366eef1..91560a3 100644
--- a/src/metrics.rs
+++ b/src/metrics.rs
@@ -285,6 +285,9 @@ impl TextMetrics {
     }
 
     pub(crate) fn width_until(&self, font_size: f32, letter_spacing: f32, index: usize) -> f32 {
+        if self.units == 0 {
+            return 0.0;
+        }
         let factor = font_size / self.units as f32;
         let positions = self.positions.read().unwrap();
         positions.iter().take(index).fold(0.0, |current, p| {