diff --git a/.github/workflows/test-windows.yml b/.github/workflows/test-windows.yml
index d53daec1365..2b15d6aea3c 100644
--- a/.github/workflows/test-windows.yml
+++ b/.github/workflows/test-windows.yml
@@ -68,8 +68,8 @@ jobs:
     - name: Install dependencies
       id: install
       run: |
-        7z x winbuild\depends\nasm-2.14.02-win64.zip "-o$env:RUNNER_WORKSPACE\"
-        echo "$env:RUNNER_WORKSPACE\nasm-2.14.02" >> $env:GITHUB_PATH
+        7z x winbuild\depends\nasm-2.15.05-win64.zip "-o$env:RUNNER_WORKSPACE\"
+        echo "$env:RUNNER_WORKSPACE\nasm-2.15.05" >> $env:GITHUB_PATH
 
         winbuild\depends\gs9533w32.exe /S
         echo "C:\Program Files (x86)\gs\gs9.53.3\bin" >> $env:GITHUB_PATH
diff --git a/setup.py b/setup.py
index 10992779e00..2b457cf053e 100755
--- a/setup.py
+++ b/setup.py
@@ -729,7 +729,7 @@ def build_extensions(self):
             defs.append(("HAVE_LIBTIFF", None))
             # FIXME the following define should be detected automatically
             #       based on system libtiff, see #4237
-            if PLATFORM_MINGW:
+            if sys.platform == "win32":
                 defs.append(("USE_WIN32_FILEIO", None))
         if feature.xcb:
             libs.append(feature.xcb)
diff --git a/winbuild/tiff.opt b/winbuild/tiff.opt
index d82c51678d6..d6e7a8ed43d 100644
--- a/winbuild/tiff.opt
+++ b/winbuild/tiff.opt
@@ -124,7 +124,7 @@ OPTFLAGS =	/Ox /MD /EHsc /W3 /D_CRT_SECURE_NO_DEPRECATE
 # instead of Windows specific system calls. See notes on top of tif_unix.c
 # module for details.
 #
-USE_WIN_CRT_LIB = 1
+#USE_WIN_CRT_LIB = 1
 
 # Compiler specific options. You may probably want to adjust compilation
 # parameters in CFLAGS variable. Refer to your compiler documentation