diff --git a/src/KSPACE/ewald.cpp b/src/KSPACE/ewald.cpp
index 04ebd7eb82..e6e4863c57 100644
--- a/src/KSPACE/ewald.cpp
+++ b/src/KSPACE/ewald.cpp
@@ -94,7 +94,7 @@ void Ewald::init()
 
   if (slabflag == 0 && domain->nonperiodic > 0)
     error->all(FLERR,"Cannot use nonperiodic boundaries with Ewald");
-  if (slabflag == 1) {
+  if (slabflag) {
     if (domain->xperiodic != 1 || domain->yperiodic != 1 ||
         domain->boundary[2][0] != 1 || domain->boundary[2][1] != 1)
       error->all(FLERR,"Incorrect boundaries with slab Ewald");
@@ -382,7 +382,7 @@ void Ewald::compute(int eflag, int vflag)
   for (i = 0; i < nlocal; i++) {
     f[i][0] += qscale * q[i]*ek[i][0];
     f[i][1] += qscale * q[i]*ek[i][1];
-    f[i][2] += qscale * q[i]*ek[i][2];
+    if (slabflag != 2) f[i][2] += qscale * q[i]*ek[i][2];
   }
 
   // global energy
@@ -426,7 +426,7 @@ void Ewald::compute(int eflag, int vflag)
 
   // 2d slab correction
 
-  if (slabflag) slabcorr();
+  if (slabflag == 1) slabcorr();
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/KSPACE/pppm.cpp b/src/KSPACE/pppm.cpp
index a4aed0f3a7..47c644702e 100644
--- a/src/KSPACE/pppm.cpp
+++ b/src/KSPACE/pppm.cpp
@@ -131,7 +131,7 @@ void PPPM::init()
 
   if (slabflag == 0 && domain->nonperiodic > 0)
     error->all(FLERR,"Cannot use nonperiodic boundaries with PPPM");
-  if (slabflag == 1) {
+  if (slabflag) {
     if (domain->xperiodic != 1 || domain->yperiodic != 1 ||
         domain->boundary[2][0] != 1 || domain->boundary[2][1] != 1)
       error->all(FLERR,"Incorrect boundaries with slab PPPM");
@@ -800,7 +800,7 @@ void PPPM::compute(int eflag, int vflag)
 
   // 2d slab correction
 
-  if (slabflag) slabcorr();
+  if (slabflag == 1) slabcorr();
 
   // convert atoms back from lamda to box coords
 
@@ -2247,7 +2247,7 @@ void PPPM::fieldforce()
     const double qfactor = force->qqrd2e * scale * q[i];
     f[i][0] += qfactor*ekx;
     f[i][1] += qfactor*eky;
-    f[i][2] += qfactor*ekz;
+    if (slabflag != 2) f[i][2] += qfactor*ekz;
   }
 }
 
diff --git a/src/kspace.cpp b/src/kspace.cpp
index 61fa8e400d..61a2b0e9a6 100644
--- a/src/kspace.cpp
+++ b/src/kspace.cpp
@@ -189,14 +189,18 @@ void KSpace::modify_params(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"slab") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal kspace_modify command");
-      slab_volfactor = atof(arg[iarg+1]);
+      if (strcmp(arg[iarg+1],"nozforce") == 0) {
+        slabflag = 2;
+      } else {
+        slabflag = 1;
+        slab_volfactor = atof(arg[iarg+1]);
+        if (slab_volfactor <= 1.0)
+          error->all(FLERR,"Bad kspace_modify slab parameter");
+        if (slab_volfactor < 2.0 && comm->me == 0)
+          error->warning(FLERR,"Kspace_modify slab param < 2.0 may "
+                         "cause unphysical behavior");
+      }
       iarg += 2;
-      if (slab_volfactor <= 1.0)
-        error->all(FLERR,"Bad kspace_modify slab parameter");
-      if (slab_volfactor < 2.0 && comm->me == 0)
-        error->warning(FLERR,"Kspace_modify slab param < 2.0 may "
-                       "cause unphysical behavior");
-      slabflag = 1;
     } else if (strcmp(arg[iarg],"compute") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal kspace_modify command");
       if (strcmp(arg[iarg+1],"yes") == 0) compute_flag = 1;