diff --git a/test-suite/src/main/scala/testsuite/core/HijackedClassesDispatchTest.scala b/test-suite/src/main/scala/testsuite/core/HijackedClassesDispatchTest.scala
index 9f273b7b..0f191968 100644
--- a/test-suite/src/main/scala/testsuite/core/HijackedClassesDispatchTest.scala
+++ b/test-suite/src/main/scala/testsuite/core/HijackedClassesDispatchTest.scala
@@ -12,7 +12,7 @@ object HijackedClassesDispatchTest {
       testToString(true, "true") &&
         testToString(54321, "54321") &&
         testToString(obj, "Test class") &&
-        testToString(obj2, "[object]") &&
+        testToStringStartsWith(obj2, "testsuite.core.HijackedClassesDispatchTest$Test2@") &&
         testToString('A', "A") &&
         testHashCode(true, 1231) &&
         testHashCode(54321, 54321) &&
@@ -43,6 +43,9 @@ object HijackedClassesDispatchTest {
   def testToString(x: Any, expected: String): Boolean =
     x.toString() == expected
 
+  def testToStringStartsWith(x: Any, expectedPrefix: String): Boolean =
+    x.toString().startsWith(expectedPrefix)
+
   def testHashCode(x: Any, expected: Int): Boolean =
     x.hashCode() == expected
 
diff --git a/wasm/src/main/scala/ir2wasm/LibraryPatches.scala b/wasm/src/main/scala/ir2wasm/LibraryPatches.scala
index b14feb4e..2b26e7e8 100644
--- a/wasm/src/main/scala/ir2wasm/LibraryPatches.scala
+++ b/wasm/src/main/scala/ir2wasm/LibraryPatches.scala
@@ -17,125 +17,25 @@ import wasm.utils.MemClassDefIRFile
 /** Patches that we apply to the standard library classes to make them wasm-friendly. */
 object LibraryPatches {
   def patchIRFiles(irFiles: Seq[IRFile])(implicit ec: ExecutionContext): Future[Seq[IRFile]] = {
-    val derivedCharBox = new java.util.concurrent.atomic.AtomicReference[IRFile](null)
-    val derivedLongBox = new java.util.concurrent.atomic.AtomicReference[IRFile](null)
-
-    val patched1: Future[Seq[IRFile]] = Future.traverse(irFiles) { irFile =>
+    val derivedIRFiles: Future[Seq[Option[IRFile]]] = Future.traverse(irFiles) { irFile =>
       val irFileImpl = IRFileImpl.fromIRFile(irFile)
       irFileImpl.entryPointsInfo.flatMap { entryPointsInfo =>
-        MethodPatches.get(entryPointsInfo.className) match {
-          case None =>
-            entryPointsInfo.className match {
-              case BoxedCharacterClass | BoxedLongClass =>
-                irFileImpl.tree.map { classDef =>
-                  val derivedBox = MemClassDefIRFile(deriveBoxClass(classDef))
-                  if (classDef.className == BoxedCharacterClass)
-                    derivedCharBox.set(derivedBox)
-                  else
-                    derivedLongBox.set(derivedBox)
-                  irFile
-                }
-              case _ =>
-                Future.successful(irFile)
+        entryPointsInfo.className match {
+          case BoxedCharacterClass | BoxedLongClass =>
+            irFileImpl.tree.map { classDef =>
+              Some(MemClassDefIRFile(deriveBoxClass(classDef)))
             }
-          case Some(patches) =>
-            irFileImpl.tree.map(classDef => MemClassDefIRFile(applyMethodPatches(classDef, patches)))
+          case _ =>
+            Future.successful(None)
         }
       }
     }
 
-    patched1.map { irFiles1 =>
-      val extra = List(FloatingPointBitsIRFile, derivedCharBox.get(), derivedLongBox.get())
-      extra ++ irFiles1
+    derivedIRFiles.map { derived =>
+      derived.flatten ++ irFiles
     }
   }
 
-  private val FloatingPointBitsIRFile: IRFile = {
-    val classDef = ClassDef(
-      ClassIdent("java.lang.FloatingPointBits$"),
-      NON,
-      ModuleClass,
-      None,
-      Some(ClassIdent(ObjectClass)),
-      Nil,
-      None,
-      None,
-      Nil,
-      List(
-        trivialCtor("java.lang.FloatingPointBits$"),
-        MethodDef(
-          EMF, MethodIdent(m("numberHashCode", List(D), I)), NON,
-          List(paramDef("value", DoubleType)), IntType,
-          Some(Block(
-            // TODO This is not a compliant but it's good enough for now
-            UnaryOp(UnaryOp.DoubleToInt, VarRef("value")(DoubleType))
-          ))
-        )(EOH, NOV)
-      ),
-      None,
-      Nil,
-      Nil,
-      Nil
-    )(EOH)
-
-    MemClassDefIRFile(classDef)
-  }
-
-  private val MethodPatches: Map[ClassName, List[MethodDef]] = {
-    Map(
-      ObjectClass -> List(
-        // TODO Remove this patch when we support getClass() and full string concatenation
-        MethodDef(
-          EMF, m("toString", Nil, T), NON,
-          Nil, ClassType(BoxedStringClass),
-          Some(StringLiteral("[object]"))
-        )(EOH, NOV)
-      ),
-
-      BoxedCharacterClass.withSuffix("$") -> List(
-        MethodDef(
-          EMF, m("toString", List(C), T), NON,
-          List(paramDef("c", CharType)), ClassType(BoxedStringClass),
-          Some(BinaryOp(BinaryOp.String_+, StringLiteral(""), VarRef("c")(CharType)))
-        )(EOH, NOV)
-      ),
-
-      BoxedIntegerClass.withSuffix("$") -> List(
-        MethodDef(
-          EMF, m("toHexString", List(I), T), NON,
-          List(paramDef("i", IntType)), ClassType(BoxedStringClass),
-          Some(
-            // TODO Write a compliant implementation
-            BinaryOp(BinaryOp.String_+, StringLiteral(""), VarRef("i")(IntType))
-          )
-        )(EOH, NOV)
-      )
-    )
-  }
-
-  private def applyMethodPatches(classDef: ClassDef, patches: List[MethodDef]): ClassDef = {
-    val patchesMap = patches.map(m => m.name.name -> m).toMap
-    val patchedMethods = classDef.methods.map(m => patchesMap.getOrElse(m.name.name, m))
-
-    import classDef._
-    ClassDef(
-      name,
-      originalName,
-      kind,
-      jsClassCaptures,
-      superClass,
-      interfaces,
-      jsSuperClass,
-      jsNativeLoadSpec,
-      fields,
-      patchedMethods,
-      jsConstructor,
-      jsMethodProps,
-      jsNativeMembers,
-      topLevelExportDefs
-    )(EOH)(pos)
-  }
-
   /** Generates the accompanying Box class of `Character` or `Long`.
    *
    *  These box classes will be used as the generic representation of `char`s
diff --git a/wasm/src/main/scala/ir2wasm/WasmExpressionBuilder.scala b/wasm/src/main/scala/ir2wasm/WasmExpressionBuilder.scala
index fb094149..ad9ec753 100644
--- a/wasm/src/main/scala/ir2wasm/WasmExpressionBuilder.scala
+++ b/wasm/src/main/scala/ir2wasm/WasmExpressionBuilder.scala
@@ -697,7 +697,7 @@ private class WasmExpressionBuilder private (
       case CharToInt | ByteToInt | ShortToInt =>
         () // these are no-ops because they are all represented as i32's with the right mathematical value
       case IntToLong =>
-        instrs += I64_EXTEND32_S
+        instrs += I64_EXTEND_I32_S
       case IntToDouble =>
         instrs += F64_CONVERT_I32_S
       case FloatToDouble =>