diff --git a/lightmotif/src/pwm.rs b/lightmotif/src/pwm.rs
index f00a926a3f5ece7cdb01cefd2c31a3ee84e834db..a56cabb7d1fbf68fe956be36977c8bdec1512c8b 100644
--- a/lightmotif/src/pwm.rs
+++ b/lightmotif/src/pwm.rs
@@ -291,7 +291,7 @@ impl<A: Alphabet> FrequencyMatrix<A> {
                 if f <= 0.0 {
                     dst[j] = f32::NEG_INFINITY;
                 } else {
-                    dst[j] = (x / f).log2();
+                    dst[j] = x.log2() - f.log2();
                 }
             }
         }