diff --git a/src/msckf_vio.cpp b/src/msckf_vio.cpp
index 0990c45..965484d 100644
--- a/src/msckf_vio.cpp
+++ b/src/msckf_vio.cpp
@@ -1047,7 +1047,7 @@ void MsckfVio::PhotometricMeasurementJacobian(
 
     //d{}^Gp_P{ij} / \rho_i
     double rho = feature.anchor_rho;
-    dGpi_drhoj = feature.T_anchor_w.linear() * Eigen::Vector3d(-feature.anchorPatch_ideal[count].x/(rho*rho), -feature.anchorPatch_ideal[count].y/(rho*rho), 1/(rho*rho));
+    dGpi_drhoj = feature.T_anchor_w.linear() * Eigen::Vector3d(-feature.anchorPatch_ideal[count].x/(rho*rho), -feature.anchorPatch_ideal[count].y/(rho*rho), -1/(rho*rho));
 
     dGpi_XpAj.block<3, 3>(0, 0) = skewSymmetric(Eigen::Vector3d(feature.anchorPatch_ideal[count].x/(rho), feature.anchorPatch_ideal[count].y/(rho), 1/(rho)));
     dGpi_XpAj.block<3, 3>(0, 3) = Matrix<double, 3, 3>::Identity();