diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 58f851aea3817..62ae8d855897e 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -284,6 +284,10 @@ impl EmitterWriter {
                           line: &Line,
                           width_offset: usize,
                           code_offset: usize) -> Vec<(usize, Style)> {
+        if line.line_index == 0 {
+            return Vec::new();
+        }
+
         let source_string = match file.get_line(line.line_index - 1) {
             Some(s) => s,
             None => return Vec::new(),