diff --git a/doc/src/compute_fabric.rst b/doc/src/compute_fabric.rst
index 87fabe2374..77586e617a 100644
--- a/doc/src/compute_fabric.rst
+++ b/doc/src/compute_fabric.rst
@@ -119,7 +119,7 @@ as
 
 .. math::
 
-   F^t_{ab}  =  \frac{15}{3\, \mathrm{Tr}(N)} (T_{ab} - \frac{1}{3} \mathrm{Tr}(T) \delta_{ab})
+   F^t_{ab}  =  \frac{5}{\mathrm{Tr}(N)} (T_{ab} - \frac{1}{3} \mathrm{Tr}(T) \delta_{ab})
 
 where the tensor :math:`T` is defined as
 
diff --git a/src/GRANULAR/gran_sub_mod_damping.cpp b/src/GRANULAR/gran_sub_mod_damping.cpp
index c635d90265..1ac0ce9030 100644
--- a/src/GRANULAR/gran_sub_mod_damping.cpp
+++ b/src/GRANULAR/gran_sub_mod_damping.cpp
@@ -130,8 +130,12 @@ void GranSubModDampingTsuji::init()
 
 double GranSubModDampingTsuji::calculate_forces()
 {
-  // in case argument < 0 due to precision issues
-  double sqrt1 = MAX(0, gm->meff * gm->Fnormal / gm->delta);
+  // in case argument <= 0 due to precision issues
+  double sqrt1;
+  if (gm->delta > 0.0)
+    sqrt1 = MAX(0.0, gm->meff * gm->Fnormal / gm->delta);
+  else
+    sqrt1 = 0.0;
   damp_prefactor = damp * sqrt(sqrt1);
   return -damp_prefactor * gm->vnnr;
 }