diff --git a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
index c6c378fb86553..7fa34cb05282d 100644
--- a/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
+++ b/mcs/class/Mono.Debugger.Soft/Mono.Debugger.Soft/Connection.cs
@@ -678,32 +678,48 @@ class PacketWriter {
 			int offset;
 
 			public PacketWriter () {
-				// FIXME:
 				data = new byte [1024];
 				offset = 0;
 			}
 
+			void MakeRoom (int size) {
+				if (offset + size >= data.Length) {
+					int new_len = data.Length * 2;
+					while (new_len < offset + size) {
+						new_len *= 2;
+					}
+					byte[] new_data = new byte [new_len];
+					Array.Copy (data, new_data, data.Length);
+					data = new_data;
+				}
+			}
+
 			public PacketWriter WriteByte (byte val) {
+				MakeRoom (1);
 				encode_byte (data, val, ref offset);
 				return this;
 			}
 
 			public PacketWriter WriteInt (int val) {
+				MakeRoom (4);
 				encode_int (data, val, ref offset);
 				return this;
 			}
 
 			public PacketWriter WriteId (long id) {
+				MakeRoom (8);
 				encode_id (data, id, ref offset);
 				return this;
 			}
 
 			public PacketWriter WriteLong (long val) {
+				MakeRoom (8);
 				encode_long (data, val, ref offset);
 				return this;
 			}
 
 			public PacketWriter WriteFloat (float f) {
+				MakeRoom (8);
 				byte[] b = DataConverter.GetBytesBE (f);
 				for (int i = 0; i < 4; ++i)
 					data [offset + i] = b [i];
@@ -712,6 +728,7 @@ class PacketWriter {
 			}
 
 			public PacketWriter WriteDouble (double d) {
+				MakeRoom (8);
 				byte[] b = DataConverter.GetBytesBE (d);
 				for (int i = 0; i < 8; ++i)
 					data [offset + i] = b [i];
@@ -734,6 +751,7 @@ class PacketWriter {
 			public PacketWriter WriteString (string s) {
 				encode_int (data, s.Length, ref offset);
 				byte[] b = Encoding.UTF8.GetBytes (s);
+				MakeRoom (b.Length);
 				Buffer.BlockCopy (b, 0, data, offset, b.Length);
 				offset += b.Length;
 				return this;
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
index 62d52df8ea84a..70ce1b8a11d60 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
@@ -3,6 +3,7 @@
 using System.Threading;
 using System.Net;
 using System.Reflection;
+using System.Text;
 using Mono.Cecil.Cil;
 using Mono.Debugger.Soft;
 using Diag = System.Diagnostics;
@@ -1654,6 +1655,12 @@ public class DebuggerTests
 		Assert.AreEqual ("ABC", s.Value);
 		Assert.AreEqual (vm.RootDomain, s.Domain);
 
+		// Long strings
+		StringBuilder sb = new StringBuilder ();
+		for (int i = 0; i < 1024; ++i)
+			sb.Append ('A');
+		s = vm.RootDomain.CreateString (sb.ToString ());
+
 		// Argument checking
 		AssertThrows <ArgumentNullException> (delegate () {
 				s = vm.RootDomain.CreateString (null);