diff --git a/opm/input/eclipse/EclipseState/Grid/FaceDir.hpp b/opm/input/eclipse/EclipseState/Grid/FaceDir.hpp
index 8200bd7ab..c5d913993 100644
--- a/opm/input/eclipse/EclipseState/Grid/FaceDir.hpp
+++ b/opm/input/eclipse/EclipseState/Grid/FaceDir.hpp
@@ -28,12 +28,13 @@ namespace Opm {
     namespace FaceDir {
 
         enum DirEnum {
-            XPlus  = 1,
-            XMinus = 2,
-            YPlus  = 4,
-            YMinus = 8,
-            ZPlus  = 16,
-            ZMinus = 32
+            Unknown = 0,
+            XPlus   = 1,
+            XMinus  = 2,
+            YPlus   = 4,
+            YMinus  = 8,
+            ZPlus   = 16,
+            ZMinus  = 32
         };
         /**
            The MULTREGTScanner will use these values as bitmaps;
diff --git a/src/opm/input/eclipse/EclipseState/Grid/FaceDir.cpp b/src/opm/input/eclipse/EclipseState/Grid/FaceDir.cpp
index a88f00708..977b7ae21 100644
--- a/src/opm/input/eclipse/EclipseState/Grid/FaceDir.cpp
+++ b/src/opm/input/eclipse/EclipseState/Grid/FaceDir.cpp
@@ -18,11 +18,11 @@
 */
 
 #include <stdexcept>
+#include <vector>
 
 #include <opm/input/eclipse/EclipseState/Grid/FaceDir.hpp>
 #include <fmt/format.h>
 
-
 namespace Opm {
 
     namespace FaceDir {
@@ -75,18 +75,23 @@ namespace Opm {
         const std::string toString(DirEnum dir)
         {
             std::vector<std::string> ret;
-            if (dir & DirEnum::XPlus)
-                ret.push_back("X+");
-            if (dir & DirEnum::XMinus)
-                ret.push_back("X-");
-            if (dir & DirEnum::YPlus)
-                ret.push_back("Y+");
-            if (dir & DirEnum::YMinus)
-                ret.push_back("Y-");
-            if (dir & DirEnum::ZPlus)
-                ret.push_back("Z+");
-            if (dir & DirEnum::ZMinus)
-                ret.push_back("Z-");
+            if (dir == DirEnum::Unknown) {
+                ret.push_back("Unknown");
+            }
+            else {
+                if (dir & DirEnum::XPlus)
+                    ret.push_back("X+");
+                if (dir & DirEnum::XMinus)
+                    ret.push_back("X-");
+                if (dir & DirEnum::YPlus)
+                    ret.push_back("Y+");
+                if (dir & DirEnum::YMinus)
+                    ret.push_back("Y-");
+                if (dir & DirEnum::ZPlus)
+                    ret.push_back("Z+");
+                if (dir & DirEnum::ZMinus)
+                    ret.push_back("Z-");
+            }
             if (ret.size() == 0)
                 throw std::runtime_error("This should not happen");
             return fmt::format("{}",fmt::join(ret, "|"));