diff --git a/iguana/struct_pb.hpp b/iguana/struct_pb.hpp
index 22cf4382..1ca54b62 100644
--- a/iguana/struct_pb.hpp
+++ b/iguana/struct_pb.hpp
@@ -346,7 +346,7 @@ inline std::string encode_pair_value(T& val, uint32_t field_no) {
   std::string temp;
   to_pb_impl<value_type>(val, field_no, temp);
   if (temp.empty()) {
-    encode_key(field_no, WireType::LengthDelimeted, temp);
+    encode_key(field_no, get_wire_type<value_type>(), temp);
     serialize_varint(0, temp);
   }
   return temp;
diff --git a/test/test.cpp b/test/test.cpp
index 65421d4e..7ac5f983 100644
--- a/test/test.cpp
+++ b/test/test.cpp
@@ -457,6 +457,25 @@ TEST_CASE("test struct_pb") {
     iguana::from_pb(st2, str);
     CHECK(st1.z == st2.z);
   }
+  {
+    message_t m{.id = 1, .t = {3, 4}};
+    test_pb_st11 st1{1, {m}, {}};
+    std::string str;
+    iguana::to_pb(st1, str);
+
+    test_pb_st11 st2;
+    iguana::from_pb(st2, str);
+    CHECK(st1.z == st2.z);
+  }
+  {
+    message_t st1{};
+    std::string str;
+    iguana::to_pb(st1, str);
+
+    message_t st2{};
+    iguana::from_pb(st2, str);
+    CHECK(st1.id == st2.id);
+  }
   {
     test_pb_st11 st1{1, {{{5, {7, 8}}}, {{9, {11, 12}}}}, {"test"}};
     std::string str;
@@ -476,6 +495,16 @@ TEST_CASE("test struct_pb") {
     iguana::from_pb(st2, str);
     CHECK(st1.z == st2.z);
   }
+  {
+    // map messages
+    test_pb_st12 st1{1, {{1, ""}, {0, "ok"}}, {{"", 4}, {"ok", 0}}};
+    std::string str;
+    iguana::to_pb(st1, str);
+
+    test_pb_st12 st2;
+    iguana::from_pb(st2, str);
+    CHECK(st1.z == st2.z);
+  }
   {
     // map messages
     test_pb_st13 st1;