diff --git a/app/src/processing/app/Sketch.java b/app/src/processing/app/Sketch.java
index bf31873bd..3663e7322 100644
--- a/app/src/processing/app/Sketch.java
+++ b/app/src/processing/app/Sketch.java
@@ -192,7 +192,7 @@ public class Sketch {
           // it would be otherwise possible to sneak in nasty filenames. [0116]
           if (Sketch.isSanitaryName(base)) {
             code[codeCount++] =
-              new SketchCode(new File(folder, filename), extension);
+              new SketchCode(new File(folder, filename));
           } else {
             editor.console.message(I18n.format("File name {0} is invalid: ignored", filename), true, false);
           }
@@ -487,7 +487,7 @@ public class Sketch {
           }
         }
 
-        if (!current.renameTo(newFile, newExtension)) {
+        if (!current.renameTo(newFile)) {
           Base.showWarning(_("Error"),
                            I18n.format(
 			     _("Could not rename \"{0}\" to \"{1}\""),
@@ -531,7 +531,7 @@ public class Sketch {
         editor.base.rebuildSketchbookMenus();
 
       } else {  // else if something besides code[0]
-        if (!current.renameTo(newFile, newExtension)) {
+        if (!current.renameTo(newFile)) {
           Base.showWarning(_("Error"),
                            I18n.format(
 			     _("Could not rename \"{0}\" to \"{1}\""),
@@ -557,7 +557,7 @@ public class Sketch {
 			 ), e);
         return;
       }
-      SketchCode newCode = new SketchCode(newFile, newExtension);
+      SketchCode newCode = new SketchCode(newFile);
       //System.out.println("new code is named " + newCode.getPrettyName() + " " + newCode.getFile());
       insertCode(newCode);
     }
@@ -788,7 +788,7 @@ public class Sketch {
 
       String pdeName = pdeFile.getPath();
       pdeName = pdeName.substring(0, pdeName.length() - 4) + ".ino";
-      return c.renameTo(new File(pdeName), "ino");
+      return c.renameTo(new File(pdeName));
     }
     return false;
   }
@@ -1075,7 +1075,7 @@ public class Sketch {
     }
 
     if (codeExtension != null) {
-      SketchCode newCode = new SketchCode(destFile, codeExtension);
+      SketchCode newCode = new SketchCode(destFile);
 
       if (replacement) {
         replaceCode(newCode);
diff --git a/app/src/processing/app/SketchCode.java b/app/src/processing/app/SketchCode.java
index 096d37875..91a8232e8 100644
--- a/app/src/processing/app/SketchCode.java
+++ b/app/src/processing/app/SketchCode.java
@@ -25,10 +25,13 @@
 package processing.app;
 
 import java.io.*;
+import java.util.List;
+import java.util.Arrays;
 
 import javax.swing.text.Document;
 
 import static processing.app.I18n._;
+import processing.app.helpers.FileUtils;
 
 
 /**
@@ -41,9 +44,6 @@ public class SketchCode {
   /** File object for where this code is located */
   private File file;
 
-  /** Extension for this file (no dots, and in lowercase). */ 
-  private String extension;
-
   /** Text of the program text for this tab */
   private String program;
 
@@ -70,9 +70,8 @@ public class SketchCode {
   private int preprocOffset;  
 
 
-  public SketchCode(File file, String extension) {
+  public SketchCode(File file) {
     this.file = file;
-    this.extension = extension;
 
     makePrettyName();
 
@@ -125,11 +124,10 @@ public class SketchCode {
   }
   
   
-  protected boolean renameTo(File what, String ext) {
+  protected boolean renameTo(File what) {
     boolean success = file.renameTo(what);
     if (success) {
       file = what;
-      extension = ext;
       makePrettyName();
     }
     return success;
@@ -151,13 +149,12 @@ public class SketchCode {
   }
   
   
-  public String getExtension() {
-    return extension;
+  public boolean isExtension(String... extensions) {
+    return isExtension(Arrays.asList(extensions));
   }
-  
-  
-  public boolean isExtension(String what) {
-    return extension.equals(what);
+
+  public boolean isExtension(List<String> extensions) {
+    return FileUtils.hasExtension(file, extensions);
   }