diff --git a/zerompk/src/lib.rs b/zerompk/src/lib.rs
index 2ac53cd..3d483cc 100644
--- a/zerompk/src/lib.rs
+++ b/zerompk/src/lib.rs
@@ -1,5 +1,8 @@
 #![no_std]
 
+#[cfg(test)]
+extern crate self as zerompk;
+
 mod consts;
 mod error;
 mod r#impl;
diff --git a/zerompk/src/read.rs b/zerompk/src/read.rs
index d56ba18..6ad361d 100644
--- a/zerompk/src/read.rs
+++ b/zerompk/src/read.rs
@@ -1477,7 +1477,31 @@ impl<'de, R: std::io::Read> Read<'de> for IOReader<R> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use crate::{Error, FromMessagePack, Read, read::IOReader, read::SliceReader};
+
+    #[allow(dead_code)]
+    #[derive(Debug, zerompk_derive::FromMessagePack)]
+    #[msgpack(map)]
+    struct DuplicateKeyMap {
+        x: u8,
+        y: u8,
+    }
+
+    #[test]
+    fn derived_map_struct_duplicate_key_restores_reader_depth() {
+        let data = [
+            0x82, // fixmap with 2 entries
+            0xa1, b'x', // fixstr of length 1: "x"
+            0x01, // positive fixint: 1
+            0xa1, b'x', // fixstr of length 1: "x" (duplicate key)
+            0x02, // positive fixint: 2
+        ];
+        let mut reader = SliceReader::new(&data);
+
+        let err = DuplicateKeyMap::read(&mut reader).unwrap_err();
+
+        assert!(matches!(err, Error::KeyDuplicated(ref key) if key == "x"));
+    }
 
     #[test]
     fn slice_reader_decrement_depth_at_zero_does_not_underflow() {
diff --git a/zerompk_derive/src/lib.rs b/zerompk_derive/src/lib.rs
index 0e5d2bd..6d84214 100644
--- a/zerompk_derive/src/lib.rs
+++ b/zerompk_derive/src/lib.rs
@@ -1128,7 +1128,7 @@ fn expand_map_struct(data: &DataStruct) -> Result<ImplBody> {
             quote! {
                 #idx => {
                     if #slot.is_some() {
-                        return Err(::zerompk::Error::KeyDuplicated(#key_name.into()));
+                        break '__zerompk_read_map Err(::zerompk::Error::KeyDuplicated(#key_name.into()));
                     }
                     #slot = ::core::option::Option::Some(#read_expr);
                 }
@@ -1167,6 +1167,7 @@ fn expand_map_struct(data: &DataStruct) -> Result<ImplBody> {
     };
 
     let read = quote! {
+        '__zerompk_read_map: {
         reader.check_map_len(#count)?;
 
         #( let mut #slots: ::core::option::Option<#tys> = ::core::option::Option::None; )*
@@ -1189,7 +1190,8 @@ fn expand_map_struct(data: &DataStruct) -> Result<ImplBody> {
             let #names = #slots.ok_or_else(|| ::zerompk::Error::KeyNotFound(#key_lits.into()))?;
         )*
 
-        Ok(Self { #( #init_fields ),* })
+        break '__zerompk_read_map Ok(Self { #( #init_fields ),* });
+        }
     };
 
     Ok(ImplBody { write, read })
@@ -1690,7 +1692,7 @@ fn build_enum_variant_payload(
                             quote! {
                                 #idx => {
                                     if #slot.is_some() {
-                                        return Err(::zerompk::Error::KeyDuplicated(#key_name.into()));
+                                        break '__zerompk_read_map Err(::zerompk::Error::KeyDuplicated(#key_name.into()));
                                     }
                                     #slot = ::core::option::Option::Some(#read_expr);
                                 }
@@ -1734,6 +1736,7 @@ fn build_enum_variant_payload(
                     };
 
                     let read_ctor = quote! {
+                        '__zerompk_read_map: {
                         reader.check_map_len(#count)?;
 
                         #( let mut #slot_vars: ::core::option::Option<#active_tys> = ::core::option::Option::None; )*
@@ -1756,7 +1759,8 @@ fn build_enum_variant_payload(
                             let #active_names = #slot_vars.ok_or_else(|| ::zerompk::Error::KeyNotFound(#key_lits.into()))?;
                         )*
 
-                        Ok(Self::#v_ident { #( #init_fields ),* })
+                        break '__zerompk_read_map Ok(Self::#v_ident { #( #init_fields ),* });
+                        }
                     };
 
                     Ok((