diff --git a/lib/potential/gkernel_triangle2d.cpp b/lib/potential/gkernel_triangle2d.cpp
index b80c3a1..466cbce 100644
--- a/lib/potential/gkernel_triangle2d.cpp
+++ b/lib/potential/gkernel_triangle2d.cpp
@@ -992,7 +992,7 @@ double gkernel_triangle2d_vx_sig(gctl::triangle2d *ele_ptr, gctl::point2dc *op_p
 
 		sum += A*(B + C);
 	}
-	return -2.0e+8*GCTL_G0*sum;
+	return 2.0e+8*GCTL_G0*sum;
 }
 
 double gkernel_triangle2d_vxx_sig(gctl::triangle2d *ele_ptr, gctl::point2dc *op_ptr)