diff --git a/appveyor.yml b/appveyor.yml
index 3e0db3a041e..a5117b047d4 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -173,7 +173,7 @@ test_script:
       git diff -U0 FETCH_HEAD...HEAD > $prDiff
       $flake8Config = "$lintSource\flake8.ini"
       $flake8Output = "$lintOutput\PR-Flake8.txt"
-      type "$prDiff" | py -m flake8 --diff --output-file="$flake8Output" --tee --config="$flake8Config"
+      type "$prDiff" | py -Xutf8 -m flake8 --diff --output-file="$flake8Output" --tee --config="$flake8Config"
       if($LastExitCode -ne 0) {
        $errorCode=$LastExitCode
        Add-AppveyorMessage "PR introduces Flake8 errors"
diff --git a/tests/lint/sconscript b/tests/lint/sconscript
index a7d9a6b0a86..ccd52a1b381 100644
--- a/tests/lint/sconscript
+++ b/tests/lint/sconscript
@@ -47,7 +47,9 @@ lintTarget = externalEnv.Command(
 	"current.diff",
 	[[
 		'type', '$SOURCE', '|',  # provide diff to stdin
-		sys.executable, "-m", "flake8",
+		sys.executable,
+		"-Xutf8",  # UTF-8 mode (PEP 540, Python >= 3.7)
+		"-m", "flake8",
 		'--diff',  # accept a unified diff from stdin
 		'--output-file=$TARGET',  # output to a file to allow easier inspection
 		'--tee',  # also output to stdout, so results appear in scons output