diff --git a/compiler/test/TestCompilerOnCharLit.kt b/compiler/test/TestCompilerOnCharLit.kt
new file mode 100644
index 000000000..2a44b34dd
--- /dev/null
+++ b/compiler/test/TestCompilerOnCharLit.kt
@@ -0,0 +1,130 @@
+package prog8tests
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.TestInstance
+import kotlin.test.*
+import kotlin.io.path.*
+
+import prog8.ast.IFunctionCall
+import prog8.ast.base.DataType
+import prog8.ast.base.VarDeclType
+import prog8.ast.expressions.IdentifierReference
+import prog8.ast.expressions.NumericLiteralValue
+import prog8.compiler.target.Cx16Target
+
+import prog8.compiler.compileProgram
+
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class TestCompilerOnCharLit {
+    val workingDir = Path("").absolute()    // Note: Path(".") does NOT work..!
+    val fixturesDir = workingDir.resolve("test/fixtures")
+    val outputDir = workingDir.resolve("build/tmp/test")
+
+    @Test
+    fun testDirectoriesSanityCheck() {
+        assertEquals("compiler", workingDir.fileName.toString())
+        assertTrue(fixturesDir.isDirectory(), "sanity check; should be directory: $fixturesDir")
+        assertTrue(outputDir.isDirectory(), "sanity check; should be directory: $outputDir")
+    }
+
+    @Test
+    fun testCharLitAsRomsubArg() {
+        val filepath = fixturesDir.resolve("charLitAsRomsubArg.p8")
+        val compilationTarget = Cx16Target
+        val result = compileProgram(
+            filepath,
+            optimize = false,
+            writeAssembly = true,
+            slowCodegenWarnings = false,
+            compilationTarget.name,
+            libdirs = listOf(),
+            outputDir
+        )
+        assertTrue(result.success, "compilation successful")
+
+        val program = result.programAst
+        val startSub = program.entrypoint()
+        val funCall = startSub.statements.filterIsInstance<IFunctionCall>()[0]
+
+        assertIs<NumericLiteralValue>(funCall.args[0],
+            "char literal should have been replaced by ubyte literal")
+        val arg = funCall.args[0] as NumericLiteralValue
+        assertEquals(DataType.UBYTE, arg.type)
+        assertEquals(compilationTarget.encodeString("\n", false)[0], arg.number)
+    }
+
+    @Test
+    fun testCharVarAsRomsubArg() {
+        val filepath = fixturesDir.resolve("charVarAsRomsubArg.p8")
+        val compilationTarget = Cx16Target
+        val result = compileProgram(
+            filepath,
+            optimize = false,
+            writeAssembly = true,
+            slowCodegenWarnings = false,
+            compilationTarget.name,
+            libdirs = listOf(),
+            outputDir
+        )
+        assertTrue(result.success, "compilation successful")
+        val program = result.programAst
+        val startSub = program.entrypoint()
+        val funCall = startSub.statements.filterIsInstance<IFunctionCall>()[0]
+
+        assertIs<IdentifierReference>(funCall.args[0])
+        val arg = funCall.args[0] as IdentifierReference
+        val decl = arg.targetVarDecl(program)!!
+        assertEquals(VarDeclType.VAR, decl.type)
+        assertEquals(DataType.UBYTE, decl.datatype)
+
+        // TODO: assertIs<CharLiteral>(decl.value,
+        //          "char literals should be kept until code gen")
+        //       val initializerValue = decl.value as CharLiteral
+        //       assertEquals('\n', (initializerValue as CharLiteral).value)
+
+        assertIs<NumericLiteralValue>(decl.value,
+            "char literal should have been replaced by ubyte literal")
+        val initializerValue = decl.value as NumericLiteralValue
+        assertEquals(DataType.UBYTE, initializerValue.type)
+        assertEquals(compilationTarget.encodeString("\n", false)[0], initializerValue.number)
+    }
+
+    @Test
+    fun testCharConstAsRomsubArg() {
+        val filepath = fixturesDir.resolve("charConstAsRomsubArg.p8")
+        val compilationTarget = Cx16Target
+        val result = compileProgram(
+            filepath,
+            optimize = false,
+            writeAssembly = true,
+            slowCodegenWarnings = false,
+            compilationTarget.name,
+            libdirs = listOf(),
+            outputDir
+        )
+        assertTrue(result.success, "compilation successful")
+        val program = result.programAst
+        val startSub = program.entrypoint()
+        val funCall = startSub.statements.filterIsInstance<IFunctionCall>()[0]
+
+        // Now, both is ok for the arg: a) still the IdRef or b) replaced by numeric literal
+        when (val arg = funCall.args[0]) {
+            is IdentifierReference -> {
+                val decl = arg.targetVarDecl(program)!!
+                assertEquals(VarDeclType.CONST, decl.type)
+                assertEquals(DataType.UBYTE, decl.datatype)
+                assertEquals(
+                    compilationTarget.encodeString("\n", false)[0],
+                    (decl.value as NumericLiteralValue).number)
+            }
+            is NumericLiteralValue -> {
+                assertEquals(
+                    compilationTarget.encodeString("\n", false)[0],
+                    arg.number)
+            }
+            else -> assertIs<IdentifierReference>(funCall.args[0]) // make test fail
+        }
+
+    }
+}
\ No newline at end of file
diff --git a/compiler/test/fixtures/charConstAsRomsubArg.p8 b/compiler/test/fixtures/charConstAsRomsubArg.p8
new file mode 100644
index 000000000..838149365
--- /dev/null
+++ b/compiler/test/fixtures/charConstAsRomsubArg.p8
@@ -0,0 +1,7 @@
+main {
+	romsub $FFD2 = chrout(ubyte ch @ A)
+	sub start() {
+		const ubyte ch = '\n'
+		chrout(ch)
+	}
+}
diff --git a/compiler/test/fixtures/charLitAsRomsubArg.p8 b/compiler/test/fixtures/charLitAsRomsubArg.p8
new file mode 100644
index 000000000..ebcfa426e
--- /dev/null
+++ b/compiler/test/fixtures/charLitAsRomsubArg.p8
@@ -0,0 +1,6 @@
+main {
+	romsub $FFD2 = chrout(ubyte ch @ A)
+	sub start() {
+		chrout('\n')
+	}
+}
diff --git a/compiler/test/fixtures/charVarAsRomsubArg.p8 b/compiler/test/fixtures/charVarAsRomsubArg.p8
new file mode 100644
index 000000000..e04462345
--- /dev/null
+++ b/compiler/test/fixtures/charVarAsRomsubArg.p8
@@ -0,0 +1,7 @@
+main {
+	romsub $FFD2 = chrout(ubyte ch @ A)
+	sub start() {
+		ubyte ch = '\n'
+		chrout(ch)
+	}
+}