diff --git a/src/test/ui/iterators/iter-count-overflow-debug.rs b/src/test/ui/iterators/iter-count-overflow-debug.rs
index 1e14142c5a67..d66120357508 100644
--- a/src/test/ui/iterators/iter-count-overflow-debug.rs
+++ b/src/test/ui/iterators/iter-count-overflow-debug.rs
@@ -1,7 +1,7 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
 // ignore-wasm32-bare compiled with panic=abort by default
-// compile-flags: -C debug_assertions=yes
+// compile-flags: -C debug_assertions=yes -C opt-level=3
 
 use std::panic;
 use std::usize::MAX;
diff --git a/src/test/ui/iterators/iter-count-overflow-ndebug.rs b/src/test/ui/iterators/iter-count-overflow-ndebug.rs
index 124aa8d22586..b755bb554f44 100644
--- a/src/test/ui/iterators/iter-count-overflow-ndebug.rs
+++ b/src/test/ui/iterators/iter-count-overflow-ndebug.rs
@@ -1,6 +1,6 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
-// compile-flags: -C debug_assertions=no
+// compile-flags: -C debug_assertions=no -C opt-level=3
 
 use std::panic;
 use std::usize::MAX;
diff --git a/src/test/ui/iterators/iter-position-overflow-debug.rs b/src/test/ui/iterators/iter-position-overflow-debug.rs
index 68e4646fe2d4..f1eded31702c 100644
--- a/src/test/ui/iterators/iter-position-overflow-debug.rs
+++ b/src/test/ui/iterators/iter-position-overflow-debug.rs
@@ -1,7 +1,7 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
 // ignore-wasm32-bare compiled with panic=abort by default
-// compile-flags: -C debug_assertions=yes
+// compile-flags: -C debug_assertions=yes -C opt-level=3
 
 use std::panic;
 use std::usize::MAX;
diff --git a/src/test/ui/iterators/iter-position-overflow-ndebug.rs b/src/test/ui/iterators/iter-position-overflow-ndebug.rs
index 3bdedf2aff1d..368f9c0c02b0 100644
--- a/src/test/ui/iterators/iter-position-overflow-ndebug.rs
+++ b/src/test/ui/iterators/iter-position-overflow-ndebug.rs
@@ -1,6 +1,6 @@
 // run-pass
 // only-32bit too impatient for 2⁶⁴ items
-// compile-flags: -C debug_assertions=no
+// compile-flags: -C debug_assertions=no -C opt-level=3
 
 use std::panic;
 use std::usize::MAX;