diff --git a/global_planner/src/gradient_path.cpp b/global_planner/src/gradient_path.cpp
index 009febecfb..caf966c352 100644
--- a/global_planner/src/gradient_path.cpp
+++ b/global_planner/src/gradient_path.cpp
@@ -264,7 +264,7 @@ bool GradientPath::getPath(float* potential, double start_x, double start_y, dou
 // calculate gradient at a cell
 // positive value are to the right and down
 float GradientPath::gradCell(float* potential, int n) {
-    if (gradx_[n] + grady_[n] > 0.0)    // check this cell
+    if (fabs(gradx_[n]) + fabs(grady_[n]) > 0.0)    // check this cell
         return 1.0;
 
     if (n < xs_ || n > xs_ * ys_ - xs_)    // would be out of bounds
diff --git a/navfn/src/navfn.cpp b/navfn/src/navfn.cpp
index 8b1fffcc3c..88e14b1be2 100644
--- a/navfn/src/navfn.cpp
+++ b/navfn/src/navfn.cpp
@@ -954,7 +954,7 @@ namespace navfn {
   float				
     NavFn::gradCell(int n)
     {
-      if (gradx[n]+grady[n] > 0.0)	// check this cell
+      if (fabs(gradx[n])+fabs(grady[n]) > 0.0)	// check this cell
         return 1.0;			
 
       if (n < nx || n > ns-nx)	// would be out of bounds