diff --git a/Buildscr b/Buildscr
index 2b789d4c..5ab0f145 100644
--- a/Buildscr
+++ b/Buildscr
@@ -232,7 +232,7 @@ in putty/windows with clangcl_a64 do Platform=arm64 make -f Makefile.clangcl BUI
 #
 # There's no installer to go with these, so they must also embed the
 # help file.
-in putty/windows with clangcl32_2003 do Platform=x86 make -f Makefile.clangcl BUILDDIR=buildold/ RCFL=-DEMBED_CHM $(Makeargs) CCTARGET=i386-pc-windows-msvc13.0.0 SUBSYSVER=,4.0 EXTRA_windows=wincrt0.obj EXTRA_console=crt0.obj EXTRA_libs=libcpmt.lib XFLAGS=/arch:IA32 all -j$(nproc)
+in putty/windows with clangcl32_2003 do Platform=x86 make -f Makefile.clangcl BUILDDIR=buildold/ RCFL=-DEMBED_CHM $(Makeargs) CCTARGET=i386-pc-windows-msvc13.0.0 SUBSYSVER=,4.0 EXTRA_windows=wincrt0.obj EXTRA_console=crt0.obj EXTRA_libs=libcpmt.lib XFLAGS="/arch:IA32 -Wno-pragma-pack" all -j$(nproc)
 
 # Remove test programs again.
 in putty/windows do make -f Makefile.clangcl BUILDDIR=build32/ cleantestprogs
diff --git a/mkfiles.pl b/mkfiles.pl
index 00112a4d..3282f359 100755
--- a/mkfiles.pl
+++ b/mkfiles.pl
@@ -549,7 +549,7 @@ if (defined $makefiles{'clangcl'}) {
                (join " ", map {"-I$dirpfx$_"} @srcdirs) .
                " /D_WINDOWS /D_WIN32_WINDOWS=0x500 /DWINVER=0x500 ".
                "/D_CRT_SECURE_NO_WARNINGS /D_WINSOCK_DEPRECATED_NO_WARNINGS").
-               " \$(PLATFORMCFLAGS)\n".
+               " -Werror \$(PLATFORMCFLAGS)\n".
     "LFLAGS = /incremental:no /dynamicbase /nxcompat\n".
     &splitline("RCPPFLAGS = ".(join " ", map {"-I$dirpfx$_"} @srcdirs).
                " -DWIN32 -D_WIN32 -DWINVER=0x0400")." \$(RCFL)\n".