diff --git a/cibuildwheel/util.py b/cibuildwheel/util.py
index f10c0ef8..79b8bd95 100644
--- a/cibuildwheel/util.py
+++ b/cibuildwheel/util.py
@@ -711,7 +711,6 @@ def parse_key_value_string(
 
     shlexer = shlex.shlex(key_value_string, posix=True, punctuation_chars=";:")
     shlexer.commenters = ""
-    shlexer.whitespace_split = True
     parts = list(shlexer)
     # parts now looks like
     # ['docker', ';', 'create_args',':', '--some-option=value', 'another-option']