diff --git a/cibuildwheel/__main__.py b/cibuildwheel/__main__.py
index 9d3e0bc5..c6c8d06f 100644
--- a/cibuildwheel/__main__.py
+++ b/cibuildwheel/__main__.py
@@ -3,6 +3,7 @@ import argparse, os, subprocess, sys, textwrap, shlex
 
 import cibuildwheel
 import cibuildwheel.linux, cibuildwheel.windows, cibuildwheel.macos
+from cibuildwheel.environment import parse_environment, EnvironmentParseError
 from cibuildwheel.util import BuildSkipper
 
 def get_option_from_environment(option_name, platform=None):
@@ -74,14 +75,13 @@ def main():
     skip_config = os.environ.get('CIBW_SKIP', '')
     environment_config = get_option_from_environment('CIBW_ENVIRONMENT', platform=platform) or ''
 
-    environment = {}
-    for key_value in shlex.split(environment_config):
-        try:
-            key, value = key_value.split('=')
-            environment[key] = value
-        except:
-            print('cibuildwheel: Malformed environment option "%s"' % key_value, file=sys.stderr)
-            exit(2)
+    try:
+        environment = parse_environment(environment_config)
+    except (EnvironmentParseError, ValueError) as e:
+        print('cibuildwheel: Malformed environment option "%s"' % key_value, file=sys.stderr)
+        import traceback
+        traceback.print_exc(None, sys.stderr)
+        exit(2)
 
     skip = BuildSkipper(skip_config)
 
diff --git a/cibuildwheel/environment.py b/cibuildwheel/environment.py
index 6d6ed71f..5b5f45e1 100644
--- a/cibuildwheel/environment.py
+++ b/cibuildwheel/environment.py
@@ -55,6 +55,9 @@ class EnvironmentAssignment(object):
     def as_shell_assignment(self):
         return 'export %s=%s' % (self.name, self.value)
 
+    def __repr__(self):
+        return '%s=%s' % (self.name, self.value)
+
 
 class ParsedEnvironment(object):
     def __init__(self, assignments):
@@ -71,3 +74,6 @@ class ParsedEnvironment(object):
 
     def as_shell_commands(self):
         return [a.as_shell_assignment() for a in self.assignments]
+
+    def __repr__(self):
+        return 'ParsedEnvironment(%r)' % [repr(a) for a in self.assignments]
diff --git a/cibuildwheel/linux.py b/cibuildwheel/linux.py
index 7e28208a..b49c4a11 100644
--- a/cibuildwheel/linux.py
+++ b/cibuildwheel/linux.py
@@ -108,9 +108,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             before_build=shlex_quote(
                 prepare_command(before_build, python='python', pip='pip') if before_build else ''
             ),
-            environment_exports=' '.join(
-                ('export %s=%s\n' % (key, shlex_quote(value)) for key, value in environment.items())
-            ),
+            environment_exports='\n'.join(environment.as_shell_commands()),
         )
 
         docker_process = subprocess.Popen([
diff --git a/cibuildwheel/macos.py b/cibuildwheel/macos.py
index e6ff34f1..5bc9ed02 100644
--- a/cibuildwheel/macos.py
+++ b/cibuildwheel/macos.py
@@ -39,6 +39,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             '/Library/Frameworks/Python.framework/Versions/%s/bin' % config.version,
             env['PATH'],
         ])
+        env = environment.as_dictionary(prev_environment=env)
 
         python = 'python3' if config.version[0] == '3' else 'python2'
         pip = 'pip3' if config.version[0] == '3' else 'pip2'
diff --git a/cibuildwheel/windows.py b/cibuildwheel/windows.py
index 1486c91b..1c7afe38 100644
--- a/cibuildwheel/windows.py
+++ b/cibuildwheel/windows.py
@@ -60,6 +60,7 @@ def build(project_dir, package_name, output_dir, test_command, test_requires, be
             os.path.join(config.path, 'Scripts'),
             env['PATH']
         ])
+        env = environment.as_dictionary(prev_environment=env)
 
         # for the logs - check we're running the right version of python
         shell(['python', '--version'], env=env)