diff --git a/lib/mesh/regular_grid.cpp b/lib/mesh/regular_grid.cpp
index b30462c..28bc240 100644
--- a/lib/mesh/regular_grid.cpp
+++ b/lib/mesh/regular_grid.cpp
@@ -1082,7 +1082,7 @@ void gctl::regular_grid::boolean(std::string newname, std::string datname, std::
 	{
 		for (size_t i = 0; i < val_ptr->size(); i++)
 		{
-			if (fabs(val_ptr2->at(i)) < 1e-8) val_ptr->at(i) = GCTL_BDL_MAX;
+			if (fabs(val_ptr2->at(i)) < 1e-8 || isnan(val_ptr2->at(i))) val_ptr->at(i) = GCTL_BDL_MAX;
 			else val_ptr->at(i) = val_ptr1->at(i);
 		}
 	}
@@ -1090,7 +1090,7 @@ void gctl::regular_grid::boolean(std::string newname, std::string datname, std::
 	{
 		for (size_t i = 0; i < val_ptr->size(); i++)
 		{
-			if (fabs(val_ptr2->at(i)) < 1e-8) val_ptr->at(i) = val_ptr1->at(i);
+			if (fabs(val_ptr2->at(i)) < 1e-8 || isnan(val_ptr2->at(i))) val_ptr->at(i) = val_ptr1->at(i);
 			else val_ptr->at(i) = GCTL_BDL_MAX;
 		}
 	}