[phobos] Why did the exe size just increase by 170K since dmd2.051?

[Don Clugston]

import std.stdio;
void main() { writefln("Hello, world!"); }

File size in Kb, Windows.
1.000  100 K
1.020  113 K
1.041  331 K
1.066  340 K
1dev   341 K

2.000   114 K
2.020   127 K
2.040   230 K
2.051   297 K
2dev    468 K  ---- !!!!!!!