diff --git a/Geo/gmshLevelset.cpp b/Geo/gmshLevelset.cpp
index e553ede60d93d4cfe9653808db8118f53d4726f0..53e6c0b404fb05ee578365b94fbbd809fcce534d 100644
--- a/Geo/gmshLevelset.cpp
+++ b/Geo/gmshLevelset.cpp
@@ -1284,7 +1284,7 @@ void gLevelsetNACA00::getClosestBndPoint(double x, double y, double z,
       if (xtb < tolr) xtb = tolr;
     }
     xb = _x0+xtb;
-    yb = (y >= _y0) ? _y0+ytb : -(_y0+ytb);
+    yb = (y >= _y0) ? _y0+ytb : _y0-ytb;
     const double norm = sqrt(1.+dyb*dyb);
     curvRad = norm*norm*norm/fabs(ddyb);
   }