diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index 34314edaf2..bdf8f3c21d 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -64,6 +64,7 @@ android {
 tasks {
     withType<KotlinCompile> {
         compilerOptions.freeCompilerArgs.addAll(
+            "-Xexpect-actual-classes",
             "-Xcontext-receivers",
             "-opt-in=kotlinx.coroutines.ExperimentalCoroutinesApi",
             "-opt-in=kotlinx.serialization.ExperimentalSerializationApi",
diff --git a/core/src/androidMain/kotlin/yokai/core/archive/ArchiveInputStream.kt b/core/src/androidMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
index 1da5acfe4a..c805145fed 100644
--- a/core/src/androidMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
+++ b/core/src/androidMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
@@ -3,6 +3,6 @@ package yokai.core.archive
 import java.io.InputStream
 
 // TODO: Use Okio's Source
-abstract class ArchiveInputStream : InputStream() {
+actual abstract class ArchiveInputStream : InputStream() {
     abstract fun getNextEntry(): ArchiveEntry?
 }
diff --git a/core/src/androidMain/kotlin/yokai/core/archive/ArchiveReader.kt b/core/src/androidMain/kotlin/yokai/core/archive/ArchiveReader.kt
index 0eb3669d49..8b7e1462bc 100644
--- a/core/src/androidMain/kotlin/yokai/core/archive/ArchiveReader.kt
+++ b/core/src/androidMain/kotlin/yokai/core/archive/ArchiveReader.kt
@@ -3,7 +3,7 @@ package yokai.core.archive
 import java.io.Closeable
 import java.io.InputStream
 
-abstract class ArchiveReader : Closeable {
+actual abstract class ArchiveReader : Closeable {
     abstract val address: Long
     abstract val size: Long
 
diff --git a/core/src/androidMain/kotlin/yokai/core/archive/ArchiveEntry.kt b/core/src/commonMain/kotlin/yokai/core/archive/ArchiveEntry.kt
similarity index 100%
rename from core/src/androidMain/kotlin/yokai/core/archive/ArchiveEntry.kt
rename to core/src/commonMain/kotlin/yokai/core/archive/ArchiveEntry.kt
diff --git a/core/src/commonMain/kotlin/yokai/core/archive/ArchiveInputStream.kt b/core/src/commonMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
new file mode 100644
index 0000000000..c4a5ff540e
--- /dev/null
+++ b/core/src/commonMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
@@ -0,0 +1,3 @@
+package yokai.core.archive
+
+expect abstract class ArchiveInputStream
diff --git a/core/src/commonMain/kotlin/yokai/core/archive/ArchiveReader.kt b/core/src/commonMain/kotlin/yokai/core/archive/ArchiveReader.kt
new file mode 100644
index 0000000000..111e11def4
--- /dev/null
+++ b/core/src/commonMain/kotlin/yokai/core/archive/ArchiveReader.kt
@@ -0,0 +1,3 @@
+package yokai.core.archive
+
+expect abstract class ArchiveReader
diff --git a/core/src/iosMain/kotlin/yokai/core/archive/ArchiveInputStream.kt b/core/src/iosMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
new file mode 100644
index 0000000000..9d85374f50
--- /dev/null
+++ b/core/src/iosMain/kotlin/yokai/core/archive/ArchiveInputStream.kt
@@ -0,0 +1,3 @@
+package yokai.core.archive
+
+actual abstract class ArchiveInputStream
diff --git a/core/src/iosMain/kotlin/yokai/core/archive/ArchiveReader.kt b/core/src/iosMain/kotlin/yokai/core/archive/ArchiveReader.kt
new file mode 100644
index 0000000000..b06f6c26d8
--- /dev/null
+++ b/core/src/iosMain/kotlin/yokai/core/archive/ArchiveReader.kt
@@ -0,0 +1,3 @@
+package yokai.core.archive
+
+actual abstract class ArchiveReader