diff --git a/src/tools/miri/src/lib.rs b/src/tools/miri/src/lib.rs
index e1d0bc1c1838..c0d1afa8023e 100644
--- a/src/tools/miri/src/lib.rs
+++ b/src/tools/miri/src/lib.rs
@@ -143,4 +143,7 @@ pub const MIRI_DEFAULT_ARGS: &[&str] = &[
     "-Zmir-keep-place-mention",
     "-Zmir-opt-level=0",
     "-Zmir-enable-passes=-CheckAlignment",
+    // Deduplicating diagnostics means we miss events when tracking what happens during an
+    // execution. Let's not do that.
+    "-Zdeduplicate-diagnostics=no",
 ];
diff --git a/src/tools/miri/tests/fail/const-ub-checks.stderr b/src/tools/miri/tests/fail/const-ub-checks.stderr
index 700a96a9062a..f6ac480f069b 100644
--- a/src/tools/miri/tests/fail/const-ub-checks.stderr
+++ b/src/tools/miri/tests/fail/const-ub-checks.stderr
@@ -10,6 +10,14 @@ note: erroneous constant encountered
 LL |     let _x = UNALIGNED_READ;
    |              ^^^^^^^^^^^^^^
 
+note: erroneous constant encountered
+  --> $DIR/const-ub-checks.rs:LL:CC
+   |
+LL |     let _x = UNALIGNED_READ;
+   |              ^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0080`.
diff --git a/src/tools/miri/tests/fail/erroneous_const2.stderr b/src/tools/miri/tests/fail/erroneous_const2.stderr
index 47b06fa8aaa0..222743670748 100644
--- a/src/tools/miri/tests/fail/erroneous_const2.stderr
+++ b/src/tools/miri/tests/fail/erroneous_const2.stderr
@@ -10,6 +10,14 @@ note: erroneous constant encountered
 LL |     println!("{}", FOO);
    |                    ^^^
 
+note: erroneous constant encountered
+  --> $DIR/erroneous_const2.rs:LL:CC
+   |
+LL |     println!("{}", FOO);
+   |                    ^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 note: erroneous constant encountered
   --> $DIR/erroneous_const2.rs:LL:CC
    |