diff --git a/vlib/v/gen/auto_str_methods.v b/vlib/v/gen/auto_str_methods.v
index 945474ec3e..d7cf3f76c0 100644
--- a/vlib/v/gen/auto_str_methods.v
+++ b/vlib/v/gen/auto_str_methods.v
@@ -55,6 +55,9 @@ fn (mut g Gen) gen_str_for_type(typ table.Type) string {
 			table.SumType {
 				g.gen_str_for_union_sum_type(sym.info, styp, str_fn_name)
 			}
+			table.Interface {
+				g.gen_str_for_interface(sym.info, styp, str_fn_name)
+			}
 			else {
 				verror("could not generate string method $str_fn_name for type '$styp'")
 			}
@@ -449,7 +452,7 @@ fn (mut g Gen) gen_str_for_struct(info table.Struct, styp string, str_fn_name st
 
 fn struct_auto_str_func(sym table.TypeSymbol, field_type table.Type, fn_name string, field_name string) string {
 	has_custom_str := sym.has_method('str')
-	if sym.kind == .enum_ {
+	if sym.kind in [.enum_, .interface_] {
 		return '${fn_name}(it.${c_name(field_name)})'
 	} else if sym.kind == .struct_ {
 		mut obj := 'it.${c_name(field_name)}'
@@ -506,6 +509,14 @@ fn (mut g Gen) gen_str_for_enum(info table.Enum, styp string, str_fn_name string
 	g.auto_str_funcs.writeln('}')
 }
 
+fn (mut g Gen) gen_str_for_interface(info table.Interface, styp string, str_fn_name string) {
+	// TODO
+	g.type_definitions.writeln('static string ${str_fn_name}($styp it); // auto')
+	g.auto_str_funcs.writeln('static string ${str_fn_name}($styp it) { /* gen_str_for_interface */')
+	g.auto_str_funcs.writeln('\treturn _SLIT("$styp{ /* TODO: Interface str */ }");')
+	g.auto_str_funcs.writeln('}')
+}
+
 fn (mut g Gen) gen_str_for_union_sum_type(info table.SumType, styp string, str_fn_name string) {
 	mut gen_fn_names := map[string]string{}
 	for typ in info.variants {
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 8b95fba826..1382188f8c 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -5483,7 +5483,7 @@ fn (g &Gen) type_to_fmt(typ table.Type) string {
 	if typ.is_ptr() && (typ.is_int() || typ.is_float()) {
 		return '%.*s\\000'
 	} else if sym.kind in
-		[.struct_, .array, .array_fixed, .map, .bool, .enum_, .sum_type, .function] {
+		[.struct_, .array, .array_fixed, .map, .bool, .enum_, .interface_, .sum_type, .function] {
 		return '%.*s\\000'
 	} else if sym.kind == .string {
 		return "\'%.*s\\000\'"
diff --git a/vlib/v/gen/str.v b/vlib/v/gen/str.v
index 80b882aeff..c0c3abc938 100644
--- a/vlib/v/gen/str.v
+++ b/vlib/v/gen/str.v
@@ -343,7 +343,7 @@ fn (mut g Gen) gen_expr_to_string(expr ast.Expr, etype table.Type) {
 			g.write('")')
 		}
 	} else if sym_has_str_method || sym.kind in
-		[.array, .array_fixed, .map, .struct_, .multi_return, .sum_type] {
+		[.array, .array_fixed, .map, .struct_, .multi_return, .sum_type, .interface_] {
 		is_ptr := typ.is_ptr()
 		str_fn_name := g.gen_str_for_type(typ)
 		if is_ptr {