diff --git a/win32/installer/hexchat-x64.skel.iss b/win32/installer/hexchat-x64.skel.iss
index 799f224f..61486190 100644
--- a/win32/installer/hexchat-x64.skel.iss
+++ b/win32/installer/hexchat-x64.skel.iss
@@ -10,6 +10,7 @@ UninstallDisplayName=HexChat (x64)
 DefaultDirName={pf}\HexChat
 DefaultGroupName=HexChat
 DisableProgramGroupPage=yes
+Compression=lzma2/ultra
 SolidCompression=yes
 SourceDir=..\rel
 OutputDir=..
diff --git a/win32/installer/hexchat-x86.skel.iss b/win32/installer/hexchat-x86.skel.iss
index 21b5efda..83a45bc7 100644
--- a/win32/installer/hexchat-x86.skel.iss
+++ b/win32/installer/hexchat-x86.skel.iss
@@ -10,6 +10,7 @@ UninstallDisplayName=HexChat (x86)
 DefaultDirName={pf}\HexChat
 DefaultGroupName=HexChat
 DisableProgramGroupPage=yes
+Compression=lzma2/ultra
 SolidCompression=yes
 SourceDir=..\rel
 OutputDir=..