diff --git a/quaternion.cpp b/quaternion.cpp
index b778036f..7b0313a3 100644
--- a/quaternion.cpp
+++ b/quaternion.cpp
@@ -118,17 +118,19 @@ cruft::slerp (quaternion<T> a, quaternion<T> b, T t)
         b      = -b;
     }
 
-    // Calculate coefficients.
-    //
-    // We previously used a linear interpolation when cosine was almost 1, but
-    // it tended to trigger assertions for normalised quaternions; feel free to
-    // change this back, but at this point performance isn't the most prominent
-    // concern.
-    T const omega = std::acos (cosine); // extract theta from dot product's cos theta
-    T const sine  = std::sin  (omega);
+    // Calculate coefficients
+    T p, q;
+    if (T(0.999999999f) > cosine) {
+        T omega = std::acos (cosine); // extract theta from dot product's cos theta
+        T sine = std::sin (omega);
 
-    T const p = std::sin ((1 - t) * omega) / sine;
-    T const q = std::sin (     t  * omega) / sine;
+        p = std::sin ((1 - t) * omega) / sine;
+        q = std::sin (     t  * omega) / sine;
+    } else {
+        // Very close, do linear interp (because it's faster)
+        p = 1 - t;
+        q =     t;
+    }
 
     return a * p + b * q;
 }