diff --git a/.appveyor.yml b/.appveyor.yml
index 461eacb4a9..03cf2f69f6 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -87,7 +87,7 @@ build_script:
              # mingw zstd doesn't come with a pkg-config file, so we manually
              # configure its flags. liblzma just works.
              #>
-            Execute-Bash "ZSTD_CFLAGS='-L/${env:compiler_path}/include' ZSTD_LIBS='-L/${env:compiler_path}/lib -lzstd' ../configure --prefix=/${env:compiler_path} --build=${env:target} --host=${env:target} --with-openssl-dir=/${env:compiler_path} --disable-asciidoc --enable-fatal-warnings ${env:hardening}"
+            Execute-Bash "ZSTD_CFLAGS='-L/${env:compiler_path}/include' ZSTD_LIBS='-L/${env:compiler_path}/lib -lzstd' ../configure --prefix=/${env:compiler_path} --build=${env:target} --host=${env:target} --with-openssl-dir=/${env:compiler_path} --disable-asciidoc --enable-fatal-warnings ${env:hardening} CFLAGS='-D__USE_MINGW_ANSI_STDIO=0'"
             Execute-Bash "V=1 make -k -j2"
             Execute-Bash "V=1 make -k -j2 install"
      }
diff --git a/changes/ticket40026 b/changes/ticket40026
new file mode 100644
index 0000000000..f87c2964e0
--- /dev/null
+++ b/changes/ticket40026
@@ -0,0 +1,3 @@
+  o Minor bugfix (CI, Windows):
+    - Don't use stdio 64 bit printf format when compiling with MINGW on
+      Appveyor. Fixes bug 40026; bugfix on 0.3.5.5-alpha.