diff --git a/gson/src/main/java/com/google/gson/FieldNamingPolicy.java b/gson/src/main/java/com/google/gson/FieldNamingPolicy.java
index 1f1eb8f1..2e833cd0 100644
--- a/gson/src/main/java/com/google/gson/FieldNamingPolicy.java
+++ b/gson/src/main/java/com/google/gson/FieldNamingPolicy.java
@@ -159,31 +159,20 @@ public enum FieldNamingPolicy implements FieldNamingStrategy {
    * Ensures the JSON field names begins with an upper case letter.
    */
   static String upperCaseFirstLetter(String name) {
-    StringBuilder fieldNameBuilder = new StringBuilder();
-    int index = 0;
-    char firstCharacter = name.charAt(index);
-    int length = name.length();
+    int firstLetterIndex = 0;
+    int limit = name.length() - 1;
+    for(; !Character.isLetter(name.charAt(firstLetterIndex)) && firstLetterIndex < limit; ++firstLetterIndex);
 
-    while (index < length - 1) {
-      if (Character.isLetter(firstCharacter)) {
-        break;
-      }
-
-      fieldNameBuilder.append(firstCharacter);
-      firstCharacter = name.charAt(++index);
-    }
-
-    if (!Character.isUpperCase(firstCharacter)) {
-      String modifiedTarget = modifyString(Character.toUpperCase(firstCharacter), name, ++index);
-      return fieldNameBuilder.append(modifiedTarget).toString();
-    } else {
+    char firstLetter = name.charAt(firstLetterIndex);
+    if(Character.isUpperCase(firstLetter)) { //The letter is already uppercased, return the original
       return name;
     }
-  }
 
-  private static String modifyString(char firstCharacter, String srcString, int indexOfSubstring) {
-    return (indexOfSubstring < srcString.length())
-        ? firstCharacter + srcString.substring(indexOfSubstring)
-        : String.valueOf(firstCharacter);
+    char uppercased = Character.toUpperCase(firstLetter);
+    if(firstLetterIndex == 0) { //First character in the string is the first letter, saves 1 substring
+      return uppercased + name.substring(1);
+    }
+
+    return name.substring(0, firstLetterIndex) + uppercased + name.substring(firstLetterIndex + 1);
   }
 }
diff --git a/gson/src/test/java/com/google/gson/functional/FieldNamingTest.java b/gson/src/test/java/com/google/gson/functional/FieldNamingTest.java
index 5d326af8..4e383ec8 100644
--- a/gson/src/test/java/com/google/gson/functional/FieldNamingTest.java
+++ b/gson/src/test/java/com/google/gson/functional/FieldNamingTest.java
@@ -33,7 +33,7 @@ public final class FieldNamingTest extends TestCase {
     Gson gson = getGsonWithNamingPolicy(IDENTITY);
     assertEquals("{'lowerCamel':1,'UpperCamel':2,'_lowerCamelLeadingUnderscore':3," +
         "'_UpperCamelLeadingUnderscore':4,'lower_words':5,'UPPER_WORDS':6," +
-        "'annotatedName':7,'lowerId':8}",
+        "'annotatedName':7,'lowerId':8,'_9':9}",
         gson.toJson(new TestNames()).replace('\"', '\''));
   }
 
@@ -41,7 +41,7 @@ public final class FieldNamingTest extends TestCase {
     Gson gson = getGsonWithNamingPolicy(UPPER_CAMEL_CASE);
     assertEquals("{'LowerCamel':1,'UpperCamel':2,'_LowerCamelLeadingUnderscore':3," +
         "'_UpperCamelLeadingUnderscore':4,'Lower_words':5,'UPPER_WORDS':6," +
-        "'annotatedName':7,'LowerId':8}",
+        "'annotatedName':7,'LowerId':8,'_9':9}",
         gson.toJson(new TestNames()).replace('\"', '\''));
   }
 
@@ -49,7 +49,7 @@ public final class FieldNamingTest extends TestCase {
     Gson gson = getGsonWithNamingPolicy(UPPER_CAMEL_CASE_WITH_SPACES);
     assertEquals("{'Lower Camel':1,'Upper Camel':2,'_Lower Camel Leading Underscore':3," +
         "'_ Upper Camel Leading Underscore':4,'Lower_words':5,'U P P E R_ W O R D S':6," +
-        "'annotatedName':7,'Lower Id':8}",
+        "'annotatedName':7,'Lower Id':8,'_9':9}",
         gson.toJson(new TestNames()).replace('\"', '\''));
   }
 
@@ -57,7 +57,7 @@ public final class FieldNamingTest extends TestCase {
     Gson gson = getGsonWithNamingPolicy(LOWER_CASE_WITH_UNDERSCORES);
     assertEquals("{'lower_camel':1,'upper_camel':2,'_lower_camel_leading_underscore':3," +
         "'__upper_camel_leading_underscore':4,'lower_words':5,'u_p_p_e_r__w_o_r_d_s':6," +
-        "'annotatedName':7,'lower_id':8}",
+        "'annotatedName':7,'lower_id':8,'_9':9}",
         gson.toJson(new TestNames()).replace('\"', '\''));
   }
 
@@ -65,7 +65,7 @@ public final class FieldNamingTest extends TestCase {
     Gson gson = getGsonWithNamingPolicy(LOWER_CASE_WITH_DASHES);
     assertEquals("{'lower-camel':1,'upper-camel':2,'_lower-camel-leading-underscore':3," +
         "'_-upper-camel-leading-underscore':4,'lower_words':5,'u-p-p-e-r_-w-o-r-d-s':6," +
-        "'annotatedName':7,'lower-id':8}",
+        "'annotatedName':7,'lower-id':8,'_9':9}",
         gson.toJson(new TestNames()).replace('\"', '\''));
   }
 
@@ -85,5 +85,6 @@ public final class FieldNamingTest extends TestCase {
     int UPPER_WORDS = 6;
     @SerializedName("annotatedName") int annotated = 7;
     int lowerId = 8;
+    int _9 = 9;
   }
 }