diff --git a/examples/simple_trainer.py b/examples/simple_trainer.py
index 8e9cb4538..617ec189d 100644
--- a/examples/simple_trainer.py
+++ b/examples/simple_trainer.py
@@ -102,7 +102,7 @@ def train(
                 self.means,
                 self.scales,
                 1,
-                self.quats,
+                self.quats / self.quats.norm(dim=-1, keepdim=True),
                 self.viewmat,
                 self.focal,
                 self.focal,
diff --git a/gsplat/cuda/csrc/helpers.cuh b/gsplat/cuda/csrc/helpers.cuh
index 0e665c2f2..4a8b3578b 100644
--- a/gsplat/cuda/csrc/helpers.cuh
+++ b/gsplat/cuda/csrc/helpers.cuh
@@ -148,13 +148,10 @@ inline __device__ float3 project_pix_vjp(
 
 inline __device__ glm::mat3 quat_to_rotmat(const float4 quat) {
     // quat to rotation matrix
-    float s = rsqrtf(
-        quat.w * quat.w + quat.x * quat.x + quat.y * quat.y + quat.z * quat.z
-    );
-    float w = quat.x * s;
-    float x = quat.y * s;
-    float y = quat.z * s;
-    float z = quat.w * s;
+    float w = quat.x;
+    float x = quat.y;
+    float y = quat.z;
+    float z = quat.w;
 
     // glm matrices are column-major
     return glm::mat3(
@@ -172,13 +169,10 @@ inline __device__ glm::mat3 quat_to_rotmat(const float4 quat) {
 
 inline __device__ float4
 quat_to_rotmat_vjp(const float4 quat, const glm::mat3 v_R) {
-    float s = rsqrtf(
-        quat.w * quat.w + quat.x * quat.x + quat.y * quat.y + quat.z * quat.z
-    );
-    float w = quat.x * s;
-    float x = quat.y * s;
-    float y = quat.z * s;
-    float z = quat.w * s;
+    float w = quat.x;
+    float x = quat.y;
+    float y = quat.z;
+    float z = quat.w;
 
     float4 v_quat;
     // v_R is COLUMN MAJOR
diff --git a/gsplat/project_gaussians.py b/gsplat/project_gaussians.py
index b41192c5b..e427f1d22 100644
--- a/gsplat/project_gaussians.py
+++ b/gsplat/project_gaussians.py
@@ -34,7 +34,7 @@ def project_gaussians(
        means3d (Tensor): xyzs of gaussians.
        scales (Tensor): scales of the gaussians.
        glob_scale (float): A global scaling factor applied to the scene.
-       quats (Tensor): rotations in quaternion [w,x,y,z] format.
+       quats (Tensor): rotations in normalized quaternion [w,x,y,z] format.
        viewmat (Tensor): view matrix for rendering.
        fx (float): focal length x.
        fy (float): focal length y.
@@ -57,6 +57,7 @@ def project_gaussians(
         - **cov3d** (Tensor): 3D covariances.
     """
     assert block_width > 1 and block_width <= 16, "block_width must be between 2 and 16"
+    assert (quats.norm(dim=-1) - 1 < 1e-6).all(), "quats must be normalized"
     return _ProjectGaussians.apply(
         means3d.contiguous(),
         scales.contiguous(),