diff --git a/java/com/google/re2j/Matcher.java b/java/com/google/re2j/Matcher.java
index 678186d0..e0f6415d 100644
--- a/java/com/google/re2j/Matcher.java
+++ b/java/com/google/re2j/Matcher.java
@@ -393,6 +393,10 @@ String substring(int start, int end) {
     return matcherInput.asCharSequence().subSequence(start, end).toString();
   }
 
+  void appendTo(Appendable sb, int end) {
+    matcherInput.appendTo(sb, appendPos, end);
+  }
+
   /** Helper for Pattern: return input length. */
   int inputLength() {
     return inputLength;
@@ -475,7 +479,7 @@ public Matcher appendReplacement(StringBuilder sb, String replacement) {
     int s = start();
     int e = end();
     if (appendPos < s) {
-      sb.append(substring(appendPos, s));
+      appendTo(sb, s);
     }
     appendPos = e;
     appendReplacementInternal(sb, replacement);
@@ -489,7 +493,7 @@ private void appendReplacementInternal(StringBuilder sb, String replacement) {
     for (; i < m - 1; i++) {
       if (replacement.charAt(i) == '\\') {
         if (last < i) {
-          sb.append(replacement.substring(last, i));
+          sb.append(replacement, last, i);
         }
         i++;
         last = i;
@@ -500,7 +504,7 @@ private void appendReplacementInternal(StringBuilder sb, String replacement) {
         if ('0' <= c && c <= '9') {
           int n = c - '0';
           if (last < i) {
-            sb.append(replacement.substring(last, i));
+            sb.append(replacement, last, i);
           }
           for (i += 2; i < m; i++) {
             c = replacement.charAt(i);
@@ -521,7 +525,7 @@ private void appendReplacementInternal(StringBuilder sb, String replacement) {
           continue;
         } else if (c == '{') {
           if (last < i) {
-            sb.append(replacement.substring(last, i));
+            sb.append(replacement, last, i);
           }
           i++; // skip {
           int j = i + 1;
@@ -552,7 +556,7 @@ private void appendReplacementInternal(StringBuilder sb, String replacement) {
    * @return the argument {@code sb}, for method chaining
    */
   public StringBuffer appendTail(StringBuffer sb) {
-    sb.append(substring(appendPos, inputLength));
+    appendTo(sb, inputLength);
     return sb;
   }
 
@@ -564,7 +568,7 @@ public StringBuffer appendTail(StringBuffer sb) {
    * @return the argument {@code sb}, for method chaining
    */
   public StringBuilder appendTail(StringBuilder sb) {
-    sb.append(substring(appendPos, inputLength));
+    appendTo(sb, inputLength);
     return sb;
   }
 
diff --git a/java/com/google/re2j/MatcherInput.java b/java/com/google/re2j/MatcherInput.java
index 8af494ba..5fcec334 100644
--- a/java/com/google/re2j/MatcherInput.java
+++ b/java/com/google/re2j/MatcherInput.java
@@ -6,6 +6,7 @@
  */
 package com.google.re2j;
 
+import java.io.IOException;
 import java.nio.charset.Charset;
 
 /**
@@ -41,6 +42,8 @@ static MatcherInput utf8(String input) {
 
   abstract Encoding getEncoding();
 
+  abstract void appendTo(Appendable sb, int beg, int end);
+
   abstract CharSequence asCharSequence();
 
   abstract byte[] asBytes();
@@ -59,6 +62,15 @@ public Encoding getEncoding() {
       return Encoding.UTF_8;
     }
 
+    @Override
+    public void appendTo(Appendable sb, int beg, int end) {
+      try {
+        sb.append(new String(bytes, beg, end - beg, "UTF-8"));
+      } catch (IOException e) {
+        throw new RuntimeException(e); // Not possible.
+      }
+    }
+
     @Override
     public CharSequence asCharSequence() {
       return new String(bytes, Charset.forName("UTF-8"));
@@ -87,6 +99,15 @@ public Encoding getEncoding() {
       return Encoding.UTF_16;
     }
 
+    @Override
+    public void appendTo(Appendable sb, int beg, int end) {
+      try {
+        sb.append(charSequence, beg, end);
+      } catch (IOException e) {
+        throw new RuntimeException(e); // Not possible.
+      }
+    }
+
     @Override
     public CharSequence asCharSequence() {
       return charSequence;