diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4164a25..90bfaa0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## v4.0.2
+- Typo / bug in EKF15 state didn't take the sqrt of the denominator in the radius of curvature calc
+
 ## v4.0.1
 - Fixed inline-ness of functions
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f199dc5..9fe9b3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.14)
 # Project information
 project(Navigation
-  VERSION 4.0.1
+  VERSION 4.0.2
   DESCRIPTION "Navigation filters and utilities"
   LANGUAGES CXX
 )
diff --git a/library.properties b/library.properties
index f0f604b..79bf1db 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=Bolder Flight Systems Navigation
-version=4.0.1
+version=4.0.2
 author=Brian Taylor <brian.taylor@bolderflight.com>
 maintainer=Brian Taylor <brian.taylor@bolderflight.com>
 sentence=Navigation and state estimation transformations, utilities, and filters.
diff --git a/src/ekf_15_state.h b/src/ekf_15_state.h
index 92180f4..c602e55 100644
--- a/src/ekf_15_state.h
+++ b/src/ekf_15_state.h
@@ -264,7 +264,7 @@ class Ekf15State {
     /* Position update */
     double denom = fabs(1.0 - (ECC2 * sin(ins_lla_rad_m_(0)) *
                   sin(ins_lla_rad_m_(0))));
-    double sqrt_denom = denom;
+    double sqrt_denom = std::sqrt(denom);
     double Rns = SEMI_MAJOR_AXIS_LENGTH_M * (1 - ECC2) /
                 (denom * sqrt_denom);
     double Rew = SEMI_MAJOR_AXIS_LENGTH_M / sqrt_denom;