diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index 54bcc64d0685..19fbbe10be9e 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -642,6 +642,7 @@ pub fn mark_incr_comp_session_as_invalid(&self) {
             IncrCompSession::Active { ref session_directory, .. } => {
                 session_directory.clone()
             }
+            IncrCompSession::InvalidBecauseOfErrors { .. } => return,
             _ => bug!("Trying to invalidate IncrCompSession `{:?}`",
                       *incr_comp_session),
         };