diff --git a/app/src/main/java/xl/model/BombCell.java b/app/src/main/java/xl/model/BombCell.java
index c8dc2b8..cacf355 100644
--- a/app/src/main/java/xl/model/BombCell.java
+++ b/app/src/main/java/xl/model/BombCell.java
@@ -15,7 +15,7 @@ public class BombCell implements Cell {
         throw XLException.ERROR_RECURSIVE;
     }
 
-    public String displayValue() {
+    public String displayValue(Environment e) {
         throw XLException.ERROR_RECURSIVE;
     }
     
diff --git a/app/src/main/java/xl/model/Cell.java b/app/src/main/java/xl/model/Cell.java
index 0971c7f..f75ff1f 100644
--- a/app/src/main/java/xl/model/Cell.java
+++ b/app/src/main/java/xl/model/Cell.java
@@ -7,6 +7,6 @@ import xl.expr.Environment;
  */
 public interface Cell {
     public double cellValue(Environment e);
-    public String displayValue();
+    public String displayValue(Environment e);
     public String formula();
 }
diff --git a/app/src/main/java/xl/model/CommentCell.java b/app/src/main/java/xl/model/CommentCell.java
index 45a98e7..c9b03ec 100644
--- a/app/src/main/java/xl/model/CommentCell.java
+++ b/app/src/main/java/xl/model/CommentCell.java
@@ -15,7 +15,7 @@ public class CommentCell implements Cell {
         return 0;
     }
 
-    public String displayValue() {
+    public String displayValue(Environment e) {
         return "# " + commentText;
     }
 
diff --git a/app/src/main/java/xl/model/ExpressionCell.java b/app/src/main/java/xl/model/ExpressionCell.java
index 630dc39..4575352 100644
--- a/app/src/main/java/xl/model/ExpressionCell.java
+++ b/app/src/main/java/xl/model/ExpressionCell.java
@@ -17,8 +17,8 @@ public class ExpressionCell implements Cell {
         return expr.value(env);
     }
 
-    public String displayValue() {
-        return Double.toString(cellValue(ENVIRON));
+    public String displayValue(Environment e) {
+        return Double.toString(cellValue(e));
     }
 
     public String formula() {
diff --git a/app/src/main/java/xl/model/XLModel.java b/app/src/main/java/xl/model/XLModel.java
index 62c3483..50a5e7b 100644
--- a/app/src/main/java/xl/model/XLModel.java
+++ b/app/src/main/java/xl/model/XLModel.java
@@ -99,7 +99,7 @@ public class XLModel extends Observable implements Environment {
 
     public void save(String path) {
         try (XLPrintStream xlPrintStream = new XLPrintStream(path)) {
-            xlPrintStream.save(map.entrySet());
+            xlPrintStream.save(this, map.entrySet());
         } catch (IOException e) {
             status = "Error saving file";
         }
@@ -107,7 +107,7 @@ public class XLModel extends Observable implements Environment {
 
     public String getAddressValue(String address) {
         if (map.containsKey(address)) {
-            return map.get(address).displayValue();
+            return map.get(address).displayValue(this);
         }
         return "";
     }
diff --git a/app/src/main/java/xl/model/XLPrintStream.java b/app/src/main/java/xl/model/XLPrintStream.java
index 3bbe6ca..869f4d2 100644
--- a/app/src/main/java/xl/model/XLPrintStream.java
+++ b/app/src/main/java/xl/model/XLPrintStream.java
@@ -3,6 +3,9 @@ package xl.model;
 import java.io.FileNotFoundException;
 import java.io.PrintStream;
 import java.util.Map.Entry;
+
+import xl.expr.Environment;
+
 import java.util.Set;
 
 /**
@@ -14,16 +17,11 @@ public class XLPrintStream extends PrintStream {
         super(fileName);
     }
 
-    public void save(Set<Entry<String, Cell>> set) {
+    public void save(Environment e, Set<Entry<String, Cell>> set) {
         for (Entry<String, Cell> entry : set) {
             print(entry.getKey());
             print('=');
-            Cell cell = entry.getValue();
-            if (cell instanceof CommentCell) {
-                println("#" + cell.displayValue());
-            } else {
-                println(cell.displayValue());
-            }
+            println(entry.getValue().displayValue(e));
         }
         flush();
         close();