diff --git a/src/core/hle/applets/mii_selector.cpp b/src/core/hle/applets/mii_selector.cpp
index 708d2f630..5191c821d 100644
--- a/src/core/hle/applets/mii_selector.cpp
+++ b/src/core/hle/applets/mii_selector.cpp
@@ -55,6 +55,11 @@ ResultCode MiiSelector::StartImpl(const Service::APT::AppletStartupParameter& pa
     // TODO(Subv): Set the expected fields in the response buffer before resending it to the application.
     // TODO(Subv): Reverse the parameter format for the Mii Selector
 
+    if(parameter.buffer_size >= sizeof(u32)) {
+        // TODO: defaults return no error, but garbage in other unknown fields
+        memset(parameter.data, 0, sizeof(u32));
+    }
+
     // Let the application know that we're closing
     Service::APT::MessageParameter message;
     message.buffer_size = parameter.buffer_size;
diff --git a/src/core/hle/applets/mii_selector.h b/src/core/hle/applets/mii_selector.h
index 6a3e7c8eb..c02dded4a 100644
--- a/src/core/hle/applets/mii_selector.h
+++ b/src/core/hle/applets/mii_selector.h
@@ -16,6 +16,50 @@
 namespace HLE {
 namespace Applets {
 
+struct MiiConfig {
+    u8  unk_000;
+    u8  unk_001;
+    u8  unk_002;
+    u8  unk_003;
+    u8  unk_004;
+    INSERT_PADDING_BYTES(3);
+    u16 unk_008;
+    INSERT_PADDING_BYTES(0x8C - 0xA);
+    u8  unk_08C;
+    INSERT_PADDING_BYTES(3);
+    u16 unk_090;
+    INSERT_PADDING_BYTES(2);
+    u32 unk_094;
+    u16 unk_098;
+    u8  unk_09A[0x64];
+    u8  unk_0FE;
+    u8  unk_0FF;
+    u32 unk_100;
+};
+
+static_assert(sizeof(MiiConfig) == 0x104, "MiiConfig structure has incorrect size");
+#define ASSERT_REG_POSITION(field_name, position) static_assert(offsetof(MiiConfig, field_name) == position, "Field "#field_name" has invalid position")
+ASSERT_REG_POSITION(unk_008, 0x08);
+ASSERT_REG_POSITION(unk_08C, 0x8C);
+ASSERT_REG_POSITION(unk_090, 0x90);
+ASSERT_REG_POSITION(unk_094, 0x94);
+ASSERT_REG_POSITION(unk_0FE, 0xFE);
+#undef ASSERT_REG_POSITION
+
+struct MiiResult {
+    u32 result_code;
+    u8 unk_04;
+    INSERT_PADDING_BYTES(7);
+    u8 unk_0C[0x60];
+    u8 unk_6C[0x16];
+    INSERT_PADDING_BYTES(2);
+};
+static_assert(sizeof(MiiResult) == 0x84, "MiiResult structure has incorrect size");
+#define ASSERT_REG_POSITION(field_name, position) static_assert(offsetof(MiiResult, field_name) == position, "Field "#field_name" has invalid position")
+ASSERT_REG_POSITION(unk_0C, 0x0C);
+ASSERT_REG_POSITION(unk_6C, 0x6C);
+#undef ASSERT_REG_POSITION
+
 class MiiSelector final : public Applet {
 public:
     MiiSelector(Service::APT::AppletId id);