diff --git a/Changelog.md b/Changelog.md
index 1274238..88bb256 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -10,6 +10,7 @@
    If you intended on adding a newline to the value, ensure you have *two* trailing newlines:
 
         echo -e "my_value\n" > /etc/container_environment/FOO
+ * It was not possible to use `docker run -e` to override environment variables defined in /etc/container_environment. This has been fixed (GH-52). Thanks to Stuart Campbell for reporting this bug.
 
 ## 0.9.9 (release date: 2014-03-25)
 
diff --git a/image/my_init b/image/my_init
index 983b65c..4a97f8e 100755
--- a/image/my_init
+++ b/image/my_init
@@ -54,7 +54,7 @@ def is_exe(path):
 	except OSError:
 		return False
 
-def import_envvars(clear_existing_environment = True):
+def import_envvars(clear_existing_environment = True, override_existing_environment = True):
 	new_env = {}
 	for envfile in listdir("/etc/container_environment"):
 		name = os.path.basename(envfile)
@@ -67,7 +67,8 @@ def import_envvars(clear_existing_environment = True):
 	if clear_existing_environment:
 		os.environ.clear()
 	for name, value in new_env.items():
-		os.environ[name] = value
+		if override_existing_environment or not name in os.environ:
+			os.environ[name] = value
 
 def export_envvars(to_dir = True):
 	shell_dump = ""
@@ -227,7 +228,7 @@ def install_insecure_key():
 	run_command_killable("/usr/sbin/enable_insecure_key")
 
 def main(args):
-	import_envvars(False)
+	import_envvars(False, False)
 	export_envvars()
 
 	if args.enable_insecure_key: