diff --git a/crates/spirv-std/src/math_ext.rs b/crates/spirv-std/src/math_ext.rs
index c5b5495d9d..bab8afdefa 100644
--- a/crates/spirv-std/src/math_ext.rs
+++ b/crates/spirv-std/src/math_ext.rs
@@ -78,7 +78,7 @@ impl MathExt for f32 {
     }
 
     fn fract(self) -> f32 {
-        self - self.trunc()
+        self - self.floor()
     }
 
     fn signum(self) -> f32 {