Why is installer compiled in Inno Setup 6 one MB larger than in Inno Setup 5

I have an Inno Setup script to make my application into an exe.

When I compile the code using Inno Setup version 6, the output file size is 110MB (as shown in Windows Explorer size column)

But when I compile the same script in Inno Setup version 5, the output file size is 109MB (1 MB smaller).

Why there is a difference in size? Is this a problem?

A compiled installer is actually an identical copy of SetupLdr.e32 with a compressed copy of Setup.e32 appended (along with actual installation files). Both these files are present in Inno Setup installation folder.

Those two files have:

• 0.68 + 2.41 MB in Inno Setup 6
• 0.11 + 1.13 MB in Inno Setup 5 Unicode
• 0.05 + 0.68 MB in Inno Setup 5 Ansi

From Inno Setup 6.0 revision history:

Delphi compiler updated from Delphi 2009 to Delphi 10.3 Rio. This change increases the size of Setup but decreases development, testing and deployment times.

This is also indirectly relevant:

Starting with Inno Setup 6 there's only one version available: Unicode Inno Setup.