diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 3bbe6a23b6628..8bcae3d9ab7cc 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -589,17 +589,6 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
     debug!("{}.structurally_relate_consts(a = {:?}, b = {:?})", relation.tag(), a, b);
     let tcx = relation.tcx();
 
-    // HACK(const_generics): We still need to eagerly evaluate consts when
-    // relating them because during `normalize_param_env_or_error`,
-    // we may relate an evaluated constant in a obligation against
-    // an unnormalized (i.e. unevaluated) const in the param-env.
-    // FIXME(generic_const_exprs): Once we always lazily unify unevaluated constants
-    // these `eval` calls can be removed.
-    if !tcx.features().generic_const_exprs {
-        a = a.eval(tcx, relation.param_env());
-        b = b.eval(tcx, relation.param_env());
-    }
-
     if tcx.features().generic_const_exprs {
         a = tcx.expand_abstract_consts(a);
         b = tcx.expand_abstract_consts(b);
diff --git a/tests/ui/consts/unnormalized-param-env.rs b/tests/ui/consts/unnormalized-param-env.rs
index a7bbe4db99290..79f6509d1aebb 100644
--- a/tests/ui/consts/unnormalized-param-env.rs
+++ b/tests/ui/consts/unnormalized-param-env.rs
@@ -1,4 +1,4 @@
-// check-pass
+// known-bug: unknown
 
 pub trait CSpace<const N: usize> {
     type Traj;
diff --git a/tests/ui/consts/unnormalized-param-env.stderr b/tests/ui/consts/unnormalized-param-env.stderr
new file mode 100644
index 0000000000000..eee098fb9a167
--- /dev/null
+++ b/tests/ui/consts/unnormalized-param-env.stderr
@@ -0,0 +1,28 @@
+error[E0277]: the trait bound `CS: CSpace<4>` is not satisfied
+  --> $DIR/unnormalized-param-env.rs:23:5
+   |
+LL | /     fn trajectory_free<TF, S1>(&self, t: &TF)
+LL | |     where
+LL | |         CS::Traj: Sized,
+LL | |         CS: CSpace<N>,
+   | |______________________^ the trait `CSpace<4>` is not implemented for `CS`
+   |
+help: consider restricting type parameter `CS`
+   |
+LL | impl<CS: CSpace<4>> Obstacle<CS, N> for ObstacleSpace2df32 {
+   |        +++++++++++
+
+error[E0277]: the trait bound `CS: CSpace<4>` is not satisfied
+  --> $DIR/unnormalized-param-env.rs:23:8
+   |
+LL |     fn trajectory_free<TF, S1>(&self, t: &TF)
+   |        ^^^^^^^^^^^^^^^ the trait `CSpace<4>` is not implemented for `CS`
+   |
+help: consider restricting type parameter `CS`
+   |
+LL | impl<CS: CSpace<4>> Obstacle<CS, N> for ObstacleSpace2df32 {
+   |        +++++++++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.