diff --git a/src/MongoDB.Bson/IO/JsonWriter.cs b/src/MongoDB.Bson/IO/JsonWriter.cs
index 4c769cb1e90..86e45c7fb94 100644
--- a/src/MongoDB.Bson/IO/JsonWriter.cs
+++ b/src/MongoDB.Bson/IO/JsonWriter.cs
@@ -814,12 +814,12 @@ protected override void Dispose(bool disposing)
         // private methods
         private string EscapedString(string value)
         {
-            if (value.All(c => !NeedsEscaping(c)))
+            if (!NeedsEscaping(value))
             {
                 return value;
             }
 
-            var sb = new StringBuilder(value.Length);
+            var sb = new StringBuilder(value.Length * 2);
 
             foreach (char c in value)
             {
@@ -935,6 +935,19 @@ private string GuidToString(BsonBinarySubType subType, byte[] bytes, GuidReprese
             }
         }
 
+        private static bool NeedsEscaping(string text)
+        {
+            foreach (var letter in text)
+            {
+                if (NeedsEscaping(letter))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
         private static bool NeedsEscaping(char c)
         {
             switch (c)