diff --git a/vec3.h b/vec3.h
index 48dfe9c..04690c7 100644
--- a/vec3.h
+++ b/vec3.h
@@ -89,7 +89,7 @@ inline Vec3 operator/(const Vec3& v, double t) {
 inline double dot(const Vec3 &u, const Vec3& v) {
     return u.e[0] * v.e[0]
          + u.e[1] * v.e[1]
-         + u.e[2] * v.e[1];
+         + u.e[2] * v.e[2];
 }
 
 inline Vec3 cross(const Vec3 &u, const Vec3& v) {