diff --git a/glm/gtx/quaternion.inl b/glm/gtx/quaternion.inl
index 1a31e947..c86ec187 100644
--- a/glm/gtx/quaternion.inl
+++ b/glm/gtx/quaternion.inl
@@ -71,9 +71,9 @@ namespace glm
 		}
 		else
 		{
-			T QuatLen = sqrt(Vec3Len * Vec3Len + q.w * q.w);
 			T t = atan(Vec3Len, T(q.w)) / Vec3Len;
-			return tquat<T, P>(log(QuatLen), t * q.x, t * q.y, t * q.z);
+			T QuatLen2 = Vec3Len * Vec3Len + q.w * q.w;
+			return tquat<T, P>(static_cast<T>(0.5) * log(QuatLen2), t * q.x, t * q.y, t * q.z);
 		}
 	}
 
diff --git a/readme.md b/readme.md
index 7f84730c..e63cb202 100644
--- a/readme.md
+++ b/readme.md
@@ -69,6 +69,9 @@ glm::mat4 camera(float Translate, glm::vec2 const & Rotate)
 - Removed GLM_LEFT_HANDED, use GLM_FORCE_LEFT_HANDED instead
 
 #### [GLM 0.9.8.1](https://github.com/g-truc/glm/tree/0.9.8) - 2016-XX-XX
+##### Improvements:
+- Optimized quaternion log function #554
+
 ##### Fixes:
 - Fixed GCC warning filtering, replaced -pedantic by -Wpedantic
 - Fixed SIMD faceforward bug. #549