diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 55c4b0e54b8..d39057cbf92 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -800,6 +800,7 @@ macro_rules! options {
         pub const parse_opt_pathbuf: Option<&str> = Some("a path");
         pub const parse_list: Option<&str> = Some("a space-separated list of strings");
         pub const parse_opt_list: Option<&str> = Some("a space-separated list of strings");
+        pub const parse_opt_comma_list: Option<&str> = Some("a comma-separated list of strings");
         pub const parse_uint: Option<&str> = Some("a number");
         pub const parse_passes: Option<&str> =
             Some("a space-separated list of passes, or `all`");
@@ -926,6 +927,18 @@ macro_rules! options {
             }
         }
 
+        fn parse_opt_comma_list(slot: &mut Option<Vec<String>>, v: Option<&str>)
+                      -> bool {
+            match v {
+                Some(s) => {
+                    let v = s.split(',').map(|s| s.to_string()).collect();
+                    *slot = Some(v);
+                    true
+                },
+                None => false,
+            }
+        }
+
         fn parse_uint(slot: &mut usize, v: Option<&str>) -> bool {
             match v.and_then(|s| s.parse().ok()) {
                 Some(i) => { *slot = i; true },