diff --git a/src/ale.cpp b/src/ale.cpp
index 7aad54961977bb63d76281ac4e5e2d405df75769..f626670333d54df0b1ce19ee0bd4423e24b2e9fd 100644
--- a/src/ale.cpp
+++ b/src/ale.cpp
@@ -172,6 +172,7 @@ namespace ale {
                             interpolate(rotations[1], times, time, interp, 0),
                             interpolate(rotations[2], times, time, interp, 0),
                             interpolate(rotations[3], times, time, interp, 0));
+    quat.normalize();
 
     Eigen::Quaterniond dQuat(interpolate(rotations[0], times, time, interp, 1),
                              interpolate(rotations[1], times, time, interp, 1),