diff --git a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
index facd69b122..f2035fd7f8 100644
--- a/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
+++ b/ir/shared/src/main/scala/org/scalajs/ir/Printers.scala
@@ -450,6 +450,9 @@ object Printers {
             case Float_fromBits  => p("<floatFromBits>(", ")")
             case Double_toBits   => p("<doubleToBits>(", ")")
             case Double_fromBits => p("<doubleFromBits>(", ")")
+
+            case Int_clz  => p("<clz>(", ")")
+            case Long_clz => p("<clz>(", ")")
           }
 
         case BinaryOp(BinaryOp.Int_-, IntLiteral(0), rhs) =>
diff --git a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
index d570445fc8..997e396530 100644
--- a/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
+++ b/ir/shared/src/test/scala/org/scalajs/ir/PrintersTest.scala
@@ -519,6 +519,9 @@ class PrintersTest {
     assertPrintEquals("<floatFromBits>(x)", UnaryOp(Float_fromBits, ref("x", IntType)))
     assertPrintEquals("<doubleToBits>(x)", UnaryOp(Double_toBits, ref("x", DoubleType)))
     assertPrintEquals("<doubleFromBits>(x)", UnaryOp(Double_fromBits, ref("x", LongType)))
+
+    assertPrintEquals("<clz>(x)", UnaryOp(Int_clz, ref("x", IntType)))
+    assertPrintEquals("<clz>(x)", UnaryOp(Long_clz, ref("x", LongType)))
   }
 
   @Test def printPseudoUnaryOp(): Unit = {
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
index f30a174597..68a5452531 100644
--- a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
+++ b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -271,6 +271,8 @@ private[optimizer] abstract class OptimizerCore(
       (lhs, rhs) match {
         case (LongType, ClassType(LongImpl.RuntimeLongClass, _)) =>
           true
+        case (ClassType(LongImpl.RuntimeLongClass, false), LongType) =>
+          true
         case (ClassType(BoxedLongClass, lhsNullable),
             ClassType(LongImpl.RuntimeLongClass, rhsNullable)) =>
           rhsNullable || !lhsNullable