diff --git a/tests/system/suite_tools/envvars b/tests/system/suite_tools/envvars
index 00aad3eab7dde282f5e8f2597f489cd170b51e37..3a6c559a87d6c4d5ea8cd42c60fda0e1e340fc9b 100644
--- a/tests/system/suite_tools/envvars
+++ b/tests/system/suite_tools/envvars
@@ -1 +1,2 @@
 QT_PLATFORM_PLUGIN=nonesuch
+LC_ALL=C
diff --git a/tests/system/suite_tools/tst_external_sort/test.py b/tests/system/suite_tools/tst_external_sort/test.py
index b9506398eab8903b8d42c0a0b6107f902bbd90aa..b3e09ddf19b121533a4642549ca083c7a3ee13c1 100644
--- a/tests/system/suite_tools/tst_external_sort/test.py
+++ b/tests/system/suite_tools/tst_external_sort/test.py
@@ -35,7 +35,10 @@ def main():
         return
     invokeMenuItem("File", "Open File or Project...")
     unsortedFile = os.path.join(os.getcwd(), "testdata", "unsorted.txt")
-    sorted = getOutputFromCmdline("sort %s" % unsortedFile).replace("\r", "")
+    locale = ""
+    if not platform.system() in ('Windows', 'Microsoft'):
+        locale = "LC_ALL=C "
+    sorted = getOutputFromCmdline("%ssort %s" % (locale, unsortedFile)).replace("\r", "")
     selectFromFileDialog(unsortedFile)
     editor = waitForObject("{type='TextEditor::PlainTextEditorWidget' unnamed='1' "
                            "visible='1' window=':Qt Creator_Core::Internal::MainWindow'}", 3000)