diff --git a/crates/epaint/src/image.rs b/crates/epaint/src/image.rs
index e14ea869..059d9d76 100644
--- a/crates/epaint/src/image.rs
+++ b/crates/epaint/src/image.rs
@@ -384,6 +384,7 @@ impl AlphaFromCoverage {
     /// Convert coverage to alpha.
     #[inline(always)]
     pub fn alpha_from_coverage(&self, coverage: f32) -> f32 {
+        let coverage = coverage.clamp(0.0, 1.0);
         match self {
             Self::Linear => coverage,
             Self::Gamma(gamma) => coverage.powf(*gamma),