diff --git a/client.diff/src/main/java/com/github/gumtreediff/client/diff/swing/MappingsPanel.java b/client.diff/src/main/java/com/github/gumtreediff/client/diff/swing/MappingsPanel.java
index 4f3d92599..7af897fcb 100644
--- a/client.diff/src/main/java/com/github/gumtreediff/client/diff/swing/MappingsPanel.java
+++ b/client.diff/src/main/java/com/github/gumtreediff/client/diff/swing/MappingsPanel.java
@@ -97,10 +97,11 @@ public MappingsPanel(String srcPath, String dstPath, TreeContext src, TreeContex
         add(split);
 
         try {
+            String charset = System.getProperty("gt.charset.decoding", "UTF-8");
             txtSrc.getUI().getEditorKit(txtSrc).read(Files.newBufferedReader(Paths.get(srcPath),
-                    Charset.forName("UTF-8")), txtSrc.getDocument(), 0);
+                    Charset.forName(charset)), txtSrc.getDocument(), 0);
             txtDst.getUI().getEditorKit(txtDst).read(Files.newBufferedReader(Paths.get(dstPath),
-                    Charset.forName("UTF-8")), txtDst.getDocument(), 0);
+                    Charset.forName(charset)), txtDst.getDocument(), 0);
         } catch (IOException | BadLocationException e) {
             e.printStackTrace();
         }
diff --git a/client.diff/src/main/java/com/github/gumtreediff/client/diff/web/HtmlDiffs.java b/client.diff/src/main/java/com/github/gumtreediff/client/diff/web/HtmlDiffs.java
index 203534184..a7cd62d2d 100644
--- a/client.diff/src/main/java/com/github/gumtreediff/client/diff/web/HtmlDiffs.java
+++ b/client.diff/src/main/java/com/github/gumtreediff/client/diff/web/HtmlDiffs.java
@@ -125,8 +125,9 @@ public void produce() throws IOException {
             }
         }
 
+        String charset = System.getProperty("gt.charset.decoding", "UTF-8");
         StringWriter w1 = new StringWriter();
-        BufferedReader r = Files.newBufferedReader(fSrc.toPath(), Charset.forName("UTF-8"));
+        BufferedReader r = Files.newBufferedReader(fSrc.toPath(), Charset.forName(charset));
         int cursor = 0;
 
         while (r.ready()) {
@@ -141,7 +142,7 @@ public void produce() throws IOException {
         srcDiff = w1.toString();
 
         StringWriter w2 = new StringWriter();
-        r = Files.newBufferedReader(fDst.toPath(), Charset.forName("UTF-8"));
+        r = Files.newBufferedReader(fDst.toPath(), Charset.forName(charset));
         cursor = 0;
 
         while (r.ready()) {
diff --git a/core/src/main/java/com/github/gumtreediff/gen/TreeGenerator.java b/core/src/main/java/com/github/gumtreediff/gen/TreeGenerator.java
index f72059401..aaea8761e 100644
--- a/core/src/main/java/com/github/gumtreediff/gen/TreeGenerator.java
+++ b/core/src/main/java/com/github/gumtreediff/gen/TreeGenerator.java
@@ -33,6 +33,8 @@ public abstract class TreeGenerator {
 
     protected abstract TreeContext generate(Reader r) throws IOException;
 
+    protected String charset = System.getProperty("gt.charset.decoding", "UTF-8");
+
     public TreeContext generateFromReader(Reader r) throws IOException {
         TreeContext ctx = generate(r);
         ctx.validate();
@@ -40,18 +42,23 @@ public TreeContext generateFromReader(Reader r) throws IOException {
     }
 
     public TreeContext generateFromFile(String path) throws IOException {
-        return generateFromReader(Files.newBufferedReader(Paths.get(path), Charset.forName("UTF-8")));
+        return generateFromReader(Files.newBufferedReader(Paths.get(path), Charset.forName(charset)));
     }
 
     public TreeContext generateFromFile(File file) throws IOException {
-        return generateFromReader(Files.newBufferedReader(file.toPath(), Charset.forName("UTF-8")));
+        return generateFromReader(Files.newBufferedReader(file.toPath(), Charset.forName(charset)));
     }
 
     public TreeContext generateFromStream(InputStream stream) throws IOException {
-        return generateFromReader(new InputStreamReader(stream, "UTF-8"));
+        return generateFromReader(new InputStreamReader(stream, charset));
     }
 
     public TreeContext generateFromString(String content) throws IOException {
         return generateFromReader(new StringReader(content));
     }
+
+    public TreeGenerator setCharset(String charset) {
+        this.charset = charset;
+        return this;
+    }
 }