diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 317b8dc205e..205ad850c0c 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -390,10 +390,11 @@ fn check_arms<'p, 'tcx>(
                 }
             }
             Useful(unreachables) => {
-                for set in unreachables {
-                    for span in set {
-                        unreachable_pattern(cx.tcx, span, id, None);
-                    }
+                let mut unreachables: Vec<_> = unreachables.into_iter().flatten().collect();
+                // Emit lints in the order in which they occur in the file.
+                unreachables.sort_unstable();
+                for span in unreachables {
+                    unreachable_pattern(cx.tcx, span, id, None);
                 }
             }
             UsefulWithWitness(_) => bug!(),
diff --git a/src/test/ui/or-patterns/exhaustiveness-unreachable-pattern.stderr b/src/test/ui/or-patterns/exhaustiveness-unreachable-pattern.stderr
index 3956a42c536..e968310d108 100644
--- a/src/test/ui/or-patterns/exhaustiveness-unreachable-pattern.stderr
+++ b/src/test/ui/or-patterns/exhaustiveness-unreachable-pattern.stderr
@@ -76,18 +76,18 @@ error: unreachable pattern
 LL |         (1 | 1,) => {}
    |              ^
 
-error: unreachable pattern
-  --> $DIR/exhaustiveness-unreachable-pattern.rs:55:15
-   |
-LL |             | 0] => {}
-   |               ^
-
 error: unreachable pattern
   --> $DIR/exhaustiveness-unreachable-pattern.rs:53:15
    |
 LL |             | 0
    |               ^
 
+error: unreachable pattern
+  --> $DIR/exhaustiveness-unreachable-pattern.rs:55:15
+   |
+LL |             | 0] => {}
+   |               ^
+
 error: unreachable pattern
   --> $DIR/exhaustiveness-unreachable-pattern.rs:63:10
    |