diff --git a/include/armadillo_bits/BaseCube_meat.hpp b/include/armadillo_bits/BaseCube_meat.hpp
index d22e479b..b3ed7572 100644
--- a/include/armadillo_bits/BaseCube_meat.hpp
+++ b/include/armadillo_bits/BaseCube_meat.hpp
@@ -261,24 +261,52 @@ BaseCube<elem_type,derived>::is_zero(const typename get_pod_type<elem_type>::res
   
   const typename ProxyCube<derived>::ea_type Pea = P.get_ea();
   
-  if(is_cx<elem_type>::yes)
+  if(tol == T(0))
     {
-    for(uword i=0; i<n_elem; ++i)
+    if(is_cx<elem_type>::yes)
       {
-      const elem_type val = Pea[i];
-      
-      const T val_real = access::tmp_real(val);
-      const T val_imag = access::tmp_imag(val);
-      
-      if(eop_aux::arma_abs(val_real) > tol)  { return false; }
-      if(eop_aux::arma_abs(val_imag) > tol)  { return false; }
+      for(uword i=0; i<n_elem; ++i)
+        {
+        const elem_type val = Pea[i];
+        
+        const T val_real = access::tmp_real(val);
+        const T val_imag = access::tmp_imag(val);
+        
+        if(eop_aux::arma_abs(val_real) != T(0))  { return false; }
+        if(eop_aux::arma_abs(val_imag) != T(0))  { return false; }
+        }
+      }
+    else  // not complex
+      {
+      for(uword i=0; i<n_elem; ++i)
+        {
+        if(eop_aux::arma_abs(Pea[i]) != T(0))  { return false; }
+        }
       }
     }
-  else  // not complex
+  else  // tol is not zero
     {
-    for(uword i=0; i < n_elem; ++i)
+    if(is_cx<elem_type>::yes)
       {
-      if(eop_aux::arma_abs(Pea[i]) > tol)  { return false; }
+      for(uword i=0; i<n_elem; ++i)
+        {
+        const elem_type val = Pea[i];
+        
+        const T val_real = access::tmp_real(val);
+        const T val_imag = access::tmp_imag(val);
+        
+        if( (eop_aux::arma_abs(val_real) > tol) || arma_isnan(val_real) )  { return false; }
+        if( (eop_aux::arma_abs(val_imag) > tol) || arma_isnan(val_imag) )  { return false; }
+        }
+      }
+    else  // not complex
+      {
+      for(uword i=0; i < n_elem; ++i)
+        {
+        const elem_type val = Pea[i];
+        
+        if( (eop_aux::arma_abs(val) > tol) || arma_isnan(val) )  { return false; }
+        }
       }
     }
   
diff --git a/include/armadillo_bits/subview_cube_meat.hpp b/include/armadillo_bits/subview_cube_meat.hpp
index 76b4ae96..657c2c68 100644
--- a/include/armadillo_bits/subview_cube_meat.hpp
+++ b/include/armadillo_bits/subview_cube_meat.hpp
@@ -1395,18 +1395,21 @@ subview_cube<eT>::is_zero(const typename get_pod_type<eT>::result tol) const
   {
   arma_debug_sigprint();
   
+  typedef typename get_pod_type<elem_type>::result T;
+  
+  arma_conform_check( (tol < T(0)), "is_zero(): parameter 'tol' must be >= 0" );
+  
   const uword local_n_rows   = n_rows;
   const uword local_n_cols   = n_cols;
   const uword local_n_slices = n_slices;
   
-  if( (local_n_rows != 0) && (local_n_cols != 0) )
+  if( (local_n_rows == 0) || (local_n_cols == 0) || (local_n_slices == 0) )  { return false; }
+  
+  for(uword slice = 0; slice < local_n_slices; ++slice)
     {
-    for(uword slice = 0; slice < local_n_slices; ++slice)
+    for(uword col = 0; col < local_n_cols; ++col)
       {
-      for(uword col = 0; col < local_n_cols; ++col)
-        {
-        if(arrayops::is_zero(slice_colptr(slice,col), local_n_rows, tol) == false)  { return false; }
-        }
+      if(arrayops::is_zero(slice_colptr(slice,col), local_n_rows, tol) == false)  { return false; }
       }
     }