diff --git a/ci.sh b/ci.sh
index 12683a2fccbe..56a6f1228ab5 100755
--- a/ci.sh
+++ b/ci.sh
@@ -25,8 +25,7 @@ function run_tests {
   ./miri test --locked
   if ! [ -n "${MIRI_TEST_TARGET+exists}" ]; then
     # Only for host architecture: tests with MIR optimizations
-    # FIXME: only testing level 2 because of <https://github.com/rust-lang/rust/issues/76432>.
-    MIRIFLAGS="-Z mir-opt-level=2" ./miri test --locked
+    MIRIFLAGS="-Z mir-opt-level=3" ./miri test --locked
   fi
   # "miri test" has built the sysroot for us, now this should pass without
   # any interactive questions.
diff --git a/rust-version b/rust-version
index 92bdd16b2be6..16a773193d14 100644
--- a/rust-version
+++ b/rust-version
@@ -1 +1 @@
-41507ed0d57eba71adc20a021a19b64322162f04
+a6008fac97f81a3fc51668b0c7fa0e2e6f2a599b