diff --git a/compiler/rustc_mir/src/transform/validate.rs b/compiler/rustc_mir/src/transform/validate.rs
index e1e6e71acb5a8..876ecee80c6a1 100644
--- a/compiler/rustc_mir/src/transform/validate.rs
+++ b/compiler/rustc_mir/src/transform/validate.rs
@@ -38,7 +38,9 @@ pub struct Validator {
 impl<'tcx> MirPass<'tcx> for Validator {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let def_id = body.source.def_id();
-        let param_env = tcx.param_env(def_id);
+        // We need to param_env_reveal_all_normalized, as some optimizations
+        // change types in ways that require unfolding opaque types.
+        let param_env = tcx.param_env_reveal_all_normalized(def_id);
         let mir_phase = self.mir_phase;
 
         let always_live_locals = AlwaysLiveLocals::new(body);
@@ -79,7 +81,6 @@ pub fn equal_up_to_regions(
     }
 
     // Normalize lifetimes away on both sides, then compare.
-    let param_env = param_env.with_reveal_all_normalized(tcx);
     let normalize = |ty: Ty<'tcx>| {
         tcx.normalize_erasing_regions(
             param_env,
@@ -167,17 +168,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return true;
         }
         // Normalize projections and things like that.
-        // FIXME: We need to reveal_all, as some optimizations change types in ways
-        // that require unfolding opaque types.
-        let param_env = self.param_env.with_reveal_all_normalized(self.tcx);
-        let src = self.tcx.normalize_erasing_regions(param_env, src);
-        let dest = self.tcx.normalize_erasing_regions(param_env, dest);
+        let src = self.tcx.normalize_erasing_regions(self.param_env, src);
+        let dest = self.tcx.normalize_erasing_regions(self.param_env, dest);
 
         // Type-changing assignments can happen when subtyping is used. While
         // all normal lifetimes are erased, higher-ranked types with their
         // late-bound lifetimes are still around and can lead to type
         // differences. So we compare ignoring lifetimes.
-        equal_up_to_regions(self.tcx, param_env, src, dest)
+        equal_up_to_regions(self.tcx, self.param_env, src, dest)
     }
 }
 
@@ -358,6 +356,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             }
             TerminatorKind::Call { func, args, destination, cleanup, .. } => {
                 let func_ty = func.ty(&self.body.local_decls, self.tcx);
+                let func_ty = self.tcx.normalize_erasing_regions(self.param_env, func_ty);
                 match func_ty.kind() {
                     ty::FnPtr(..) | ty::FnDef(..) => {}
                     _ => self.fail(
diff --git a/src/test/ui/issues/issue-50865-private-impl-trait/auxiliary/lib.rs b/src/test/ui/issues/issue-50865-private-impl-trait/auxiliary/lib.rs
index fb4bf2b8b44e7..f3a51b415faca 100644
--- a/src/test/ui/issues/issue-50865-private-impl-trait/auxiliary/lib.rs
+++ b/src/test/ui/issues/issue-50865-private-impl-trait/auxiliary/lib.rs
@@ -1,7 +1,3 @@
-// revisions: default miropt
-//[miropt]compile-flags: -Z mir-opt-level=2
-// ~^ This flag is for #77668, it used to be ICE.
-
 #![crate_type = "lib"]
 
 pub fn bar<P>( // Error won't happen if "bar" is not generic
diff --git a/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs b/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs
index 4d083bf232155..ccb279f7fa212 100644
--- a/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs
+++ b/src/test/ui/mir/mir-inlining/ice-issue-77306-1.rs
@@ -1,17 +1,27 @@
-// run-pass
+// Regression test for various issues related to normalization & inlining.
+// * #68347, #77306, #77668 - missed normalization during inlining.
+// * #78442 - missed normalization in validator after inlining.
+//
+// build-pass
 // compile-flags:-Zmir-opt-level=2
 
-// Previously ICEd because we did not normalize during inlining,
-// see https://github.com/rust-lang/rust/pull/77306 for more discussion.
-
 pub fn write() {
     create()()
 }
 
+pub fn write_generic<T>(_t: T) {
+    hide()();
+}
+
 pub fn create() -> impl FnOnce() {
    || ()
 }
 
+pub fn hide() -> impl Fn() {
+    write
+}
+
 fn main() {
     write();
+    write_generic(());
 }