diff --git a/CHANGELOG.md b/CHANGELOG.md
index 09df47b82f..8290ca548e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Improved performance of adjoint gradient computation for `PolySlab` and `Cylinder` geometries through vectorized sidewall patch collection (~4x speedup).
 
 ### Fixed
+- Fixed normal for `Box` shape gradient computation to always point outward from boundary which is needed for correct PEC handling.
 
 ## [2.10.0rc3] - 2025-11-26
 
diff --git a/tidy3d/components/geometry/base.py b/tidy3d/components/geometry/base.py
index a6eae24230..f83bdce265 100644
--- a/tidy3d/components/geometry/base.py
+++ b/tidy3d/components/geometry/base.py
@@ -2740,7 +2740,7 @@ def compute_integration_weight(grid_points: NDArray[float]) -> float:
         perps1 = np.zeros_like(grid_points)
         perps2 = np.zeros_like(grid_points)
 
-        normals[:, axis_normal] = 1
+        normals[:, axis_normal] = -1 if (min_max_index == 0) else 1
         perps1[:, axis_perp[0]] = 1
         perps2[:, axis_perp[1]] = 1