diff --git a/src/GRANSURF/fix_surface_global.cpp b/src/GRANSURF/fix_surface_global.cpp
index aa04801565..4acfc79256 100644
--- a/src/GRANSURF/fix_surface_global.cpp
+++ b/src/GRANSURF/fix_surface_global.cpp
@@ -254,7 +254,7 @@ FixSurfaceGlobal::FixSurfaceGlobal(LAMMPS *lmp, int narg, char **arg) :
         error->all(FLERR,"Fix surface/global smaxtype < input surf types");
       maxsurftype = smaxtype;
       iarg += 2;
-    } else if (strcmp(arg[iarg],"flag") == 0) {
+    } else if (strcmp(arg[iarg],"flat") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal fix surface/global command");
       double flat = utils::numeric(FLERR,arg[iarg+1],false,lmp);
       if (flat < 0.0 || flat > 90.0)
@@ -849,7 +849,7 @@ void FixSurfaceGlobal::post_force(int vflag)
   double dr[3],contact[3],ds[3],xc[3],vc[3],omegac[3],*forces,*torquesi;
   double *history,*allhistory,**firsthistory;
 
-  double dot, overlap, max_overlap, norm, *knorm, tmp[3];
+  double dot, overlap, max_overlap, *knorm, tmp[3];
   int it, jjtmp, connection_type, aflag, endpt_flag;
   std::unordered_set<int> *processed_contacts = new std::unordered_set<int>();
   std::map<int, int> *contacts_map = new std::map<int, int>();
@@ -1043,6 +1043,9 @@ void FixSurfaceGlobal::post_force(int vflag)
       processed_contacts->insert(j);
       force_surfs->clear();
       force_surfs->push_back(n);
+      dr[0] = contact_surfs[n].r[0];
+      dr[1] = contact_surfs[n].r[1];
+      dr[2] = contact_surfs[n].r[2];
 
       // Loop through connected surfs
       if (dimension == 2) {
@@ -1118,7 +1121,6 @@ void FixSurfaceGlobal::post_force(int vflag)
       //model->omegaj = omegasurf[j];
 
       if (force_surfs->size() != 1) {
-        norm = 0.0;
         max_overlap = 0.0;
 
         for (k = 0; k < 3; k++) {
@@ -1132,31 +1134,39 @@ void FixSurfaceGlobal::post_force(int vflag)
           m = (*force_surfs)[it];
           overlap = contact_surfs[m].overlap;
           max_overlap = MAX(max_overlap, overlap);
-          norm += overlap * overlap;
 
-          MathExtra::copy3(contact_surfs[m].r, tmp);
+          if (it == 0) {
+            // use normal vector from closest point for nearest (first) surf
+            MathExtra::copy3(contact_surfs[m].r, tmp);
+          } else {
+            // use normal vector for non-nearest surfs (extend the surf)
+            MathExtra::copy3(lines[contact_surfs[m].index].norm, tmp);
+            dot = MathExtra::dot3(contact_surfs[m].r, tmp);
+            if (dot < 0.0)
+              MathExtra::negate3(tmp);
+          }
           MathExtra::norm3(tmp);
           for (k = 0; k < 3; k++) {
             xc[k] += tmp[k] * overlap;
-            vc[k] += vsurf[contact_surfs[m].index][k] * overlap; //TODO: correct
-            omegac[k] += omegasurf[contact_surfs[m].index][k] * overlap;
+            // correct omegac, vc
           }
         }
 
-        norm = 1.0 / norm;
+
+        MathExtra::norm3(xc);
         for (k = 0; k < 3; k++) {
-          xc[k] = x[i][k] - xc[k] * max_overlap * norm;
-          vc[k] *= norm;
-          omegac[k] *= norm;
+          xc[k] = x[i][k] - xc[k] * max_overlap;
         }
+
       } else {
         m = (*force_surfs)[0];
         overlap = contact_surfs[m].overlap;
 
         for (k = 0; k < 3; k++) {
           xc[k] = x[i][k] - contact_surfs[m].r[k];
-          vc[k] = vsurf[contact_surfs[m].index][k];
-          omegac[k] = omegasurf[contact_surfs[m].index][k];
+          // correct omegac, vc
+          // vc[k] = vsurf[contact_surfs[m].index][k];
+          // omegac[k] = omegasurf[contact_surfs[m].index][k];
         }
       }