diff --git a/vlib/v/gen/c/auto_str_methods.v b/vlib/v/gen/c/auto_str_methods.v
index cc7c3c3e4f..dae5ae955b 100644
--- a/vlib/v/gen/c/auto_str_methods.v
+++ b/vlib/v/gen/c/auto_str_methods.v
@@ -384,18 +384,18 @@ fn (mut g Gen) gen_str_for_interface(info ast.Interface, styp string, str_fn_nam
 	clean_interface_v_type_name = util.strip_main_name(clean_interface_v_type_name)
 	fn_builder.writeln('static string indent_${str_fn_name}($styp x, int indent_count) { /* gen_str_for_interface */')
 	for typ in info.types {
-		subtype := g.table.sym(typ)
+		sub_sym := g.table.sym(ast.mktyp(typ))
 		mut func_name := g.get_str_fn(typ)
-		sym_has_str_method, str_method_expects_ptr, _ := subtype.str_method_info()
-		if should_use_indent_func(subtype.kind) && !sym_has_str_method {
+		sym_has_str_method, str_method_expects_ptr, _ := sub_sym.str_method_info()
+		if should_use_indent_func(sub_sym.kind) && !sym_has_str_method {
 			func_name = 'indent_$func_name'
 		}
 
 		// str_intp
 		deref := if sym_has_str_method && str_method_expects_ptr { ' ' } else { '*' }
 		if typ == ast.string_type {
-			mut val := '${func_name}(${deref}($subtype.cname*)x._$subtype.cname'
-			if should_use_indent_func(subtype.kind) && !sym_has_str_method {
+			mut val := '${func_name}(${deref}($sub_sym.cname*)x._$sub_sym.cname'
+			if should_use_indent_func(sub_sym.kind) && !sym_has_str_method {
 				val += ', indent_count'
 			}
 			val += ')'
@@ -403,11 +403,11 @@ fn (mut g Gen) gen_str_for_interface(info ast.Interface, styp string, str_fn_nam
 				{_SLIT("${clean_interface_v_type_name}(\'"), $c.si_s_code, {.d_s = $val}},
 				{_SLIT("\')"), 0, {.d_c = 0 }}
 			}))'
-			fn_builder.write_string('\tif (x._typ == _${styp}_${subtype.cname}_index)')
+			fn_builder.write_string('\tif (x._typ == _${styp}_${sub_sym.cname}_index)')
 			fn_builder.write_string(' return $res;')
 		} else {
-			mut val := '${func_name}(${deref}($subtype.cname*)x._$subtype.cname'
-			if should_use_indent_func(subtype.kind) && !sym_has_str_method {
+			mut val := '${func_name}(${deref}($sub_sym.cname*)x._$sub_sym.cname'
+			if should_use_indent_func(sub_sym.kind) && !sym_has_str_method {
 				val += ', indent_count'
 			}
 			val += ')'
@@ -415,7 +415,7 @@ fn (mut g Gen) gen_str_for_interface(info ast.Interface, styp string, str_fn_nam
 				{_SLIT("${clean_interface_v_type_name}("), $c.si_s_code, {.d_s = $val}},
 				{_SLIT(")"), 0, {.d_c = 0 }}
 			}))'
-			fn_builder.write_string('\tif (x._typ == _${styp}_${subtype.cname}_index)')
+			fn_builder.write_string('\tif (x._typ == _${styp}_${sub_sym.cname}_index)')
 			fn_builder.write_string(' return $res;\n')
 		}
 	}
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index e0e6bf8cbb..f349bb51db 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -859,16 +859,16 @@ pub fn (mut g Gen) write_typeof_functions() {
 			g.definitions.writeln('static char * v_typeof_interface_${sym.cname}(int sidx);')
 			g.writeln('static char * v_typeof_interface_${sym.cname}(int sidx) { /* $sym.name */ ')
 			for t in inter_info.types {
-				subtype := g.table.sym(t)
-				g.writeln('\tif (sidx == _${sym.cname}_${subtype.cname}_index) return "${util.strip_main_name(subtype.name)}";')
+				sub_sym := g.table.sym(ast.mktyp(t))
+				g.writeln('\tif (sidx == _${sym.cname}_${sub_sym.cname}_index) return "${util.strip_main_name(sub_sym.name)}";')
 			}
 			g.writeln('\treturn "unknown ${util.strip_main_name(sym.name)}";')
 			g.writeln('}')
 			g.writeln('')
 			g.writeln('static int v_typeof_interface_idx_${sym.cname}(int sidx) { /* $sym.name */ ')
 			for t in inter_info.types {
-				subtype := g.table.sym(t)
-				g.writeln('\tif (sidx == _${sym.cname}_${subtype.cname}_index) return ${int(t)};')
+				sub_sym := g.table.sym(ast.mktyp(t))
+				g.writeln('\tif (sidx == _${sym.cname}_${sub_sym.cname}_index) return ${int(t)};')
 			}
 			g.writeln('\treturn ${int(ityp)};')
 			g.writeln('}')
@@ -1319,7 +1319,11 @@ pub fn (mut g Gen) write_interface_typesymbol_declaration(sym ast.TypeSymbol) {
 	g.type_definitions.writeln('\tunion {')
 	g.type_definitions.writeln('\t\tvoid* _object;')
 	for variant in info.types {
-		vcname := g.table.sym(variant).cname
+		mk_typ := ast.mktyp(variant)
+		if mk_typ != variant && mk_typ in info.types {
+			continue
+		}
+		vcname := g.table.sym(mk_typ).cname
 		g.type_definitions.writeln('\t\t$vcname* _$vcname;')
 	}
 	g.type_definitions.writeln('\t};')
@@ -2085,11 +2089,11 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 		g.expr(expr)
 		return
 	}
-	if exp_sym.info is ast.Interface && got_type_raw.idx() != expected_type.idx()
+	if exp_sym.info is ast.Interface && got_type.idx() != expected_type.idx()
 		&& !expected_type.has_flag(.optional) {
 		if expr is ast.StructInit && !got_type.is_ptr() {
 			g.inside_cast_in_heap++
-			got_styp := g.cc_type(got_type_raw.ref(), true)
+			got_styp := g.cc_type(got_type.ref(), true)
 			// TODO: why does cc_type even add this in the first place?
 			exp_styp := exp_sym.cname
 			mut fname := 'I_${got_styp}_to_Interface_$exp_styp'
@@ -2100,7 +2104,7 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 				got_styp)
 			g.inside_cast_in_heap--
 		} else {
-			got_styp := g.cc_type(got_type_raw, true)
+			got_styp := g.cc_type(got_type, true)
 			got_is_shared := got_type.has_flag(.shared_f)
 			exp_styp := if got_is_shared { '__shared__$exp_sym.cname' } else { exp_sym.cname }
 			// If it's shared, we need to use the other caster:
@@ -5334,10 +5338,10 @@ fn (mut g Gen) interface_table() string {
 		iinidx_minimum_base := 1000 // Note: NOT 0, to avoid map entries set to 0 later, so `if already_generated_mwrappers[name] > 0 {` works.
 		mut current_iinidx := iinidx_minimum_base
 		for st in inter_info.types {
-			st_sym := g.table.sym(st)
+			st_sym := g.table.sym(ast.mktyp(st))
 			// cctype is the Cleaned Concrete Type name, *without ptr*,
 			// i.e. cctype is always just Cat, not Cat_ptr:
-			cctype := g.cc_type(st, true)
+			cctype := g.cc_type(ast.mktyp(st), true)
 			$if debug_interface_table ? {
 				eprintln('>> interface name: $isym.name | concrete type: $st.debug() | st symname: $st_sym.name')
 			}
diff --git a/vlib/v/tests/cast_to_empty_interface_test.v b/vlib/v/tests/cast_to_empty_interface_test.v
new file mode 100644
index 0000000000..ac8963c14a
--- /dev/null
+++ b/vlib/v/tests/cast_to_empty_interface_test.v
@@ -0,0 +1,29 @@
+interface Any {}
+
+fn thing(any Any) string {
+	return match any {
+		int { 'int${*any:17}' }
+		f64 { 'f64${*any:20}' }
+		else { 'literal type tag?${any:10}' }
+	}
+}
+
+fn test_cast_to_empty_interface() {
+	mut ret_strings := []string{}
+	mut arr := [Any(int(11)), int(22), Any(8888), 9999, Any(f64(1.11)), f64(2.22), Any(8.88), 9.99]
+
+	for i in arr {
+		println(thing(i))
+		ret_strings << thing(i)
+	}
+
+	assert ret_strings.len == 8
+	assert ret_strings[0] == 'int               11'
+	assert ret_strings[1] == 'int               22'
+	assert ret_strings[2] == 'int             8888'
+	assert ret_strings[3] == 'int             9999'
+	assert ret_strings[4] == 'f64               1.110'
+	assert ret_strings[5] == 'f64               2.220'
+	assert ret_strings[6] == 'f64               8.880'
+	assert ret_strings[7] == 'f64               9.990'
+}