diff --git a/.github/workflows/tests_impl.yml b/.github/workflows/tests_impl.yml
index d3b1afd..4c413c2 100644
--- a/.github/workflows/tests_impl.yml
+++ b/.github/workflows/tests_impl.yml
@@ -60,7 +60,9 @@ jobs:
       with:
         tool: cargo-nextest
     - uses: actions/checkout@v4
-    - run: RUSTFLAGS="
+    - run:
+        MIRIFLAGS="-Zmiri-disable-isolation"
+        RUSTFLAGS="             
              ${{ inputs.rustflags }}
              --cfg ${{ inputs.cache_type_flag }}
              --cfg ${{ inputs.config_type_flag }}        
diff --git a/Cargo.toml b/Cargo.toml
index 347d6d4..99248da 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,6 +24,8 @@ arrayvec = { version = "0.7", optional = true }
 base64 = { version = "0.22", optional = true }
 
 [dev-dependencies]
+anyhow = "1"
+tempfile = "3"
 serde_json = "1.0"
 bincode = { version = "2.0", features = ["serde"] }
 rand = "0.8"
diff --git a/miri_test_64.bat b/miri_test_64.bat
new file mode 100644
index 0000000..749ef45
--- /dev/null
+++ b/miri_test_64.bat
@@ -0,0 +1,6 @@
+@echo off
+setlocal
+set MIRIFLAGS=-Zmiri-disable-isolation 
+set RUSTFLAGS=--cfg hisparsebitset_test_64
+cargo +nightly miri nextest run -j6 --all-features
+endlocal
\ No newline at end of file
diff --git a/src/bitset/serde.rs b/src/bitset/serde.rs
index 8ddaccb..c4e6023 100644
--- a/src/bitset/serde.rs
+++ b/src/bitset/serde.rs
@@ -1,7 +1,8 @@
+use std::fmt;
+use std::fmt::Formatter;
 use std::io::Cursor;
 use std::marker::PhantomData;
 use serde::{Deserialize, Serialize};
-use serde::de::SeqAccess;
 use crate::{BitBlock, BitSet};
 use crate::bitset::level::IBlock;
 use crate::config::Config;
@@ -20,7 +21,7 @@ impl<Conf: Config> Serialize for BitSet<Conf>{
         
         // real_len <= approx_len
         let approx_len = 
-            Conf::DataBitBlock::size()                                                 // root block
+            Conf::DataBitBlock::size()                                               // root block
             + (1 + self.level0.mask().count_ones()) * Conf::Level1BitBlock::size()   // lvl1 blocks
             + (1 + self.data.blocks().len())        * Conf::DataBitBlock::size();    // approx data blocks
         
@@ -52,48 +53,35 @@ impl<'de, Conf: Config> Deserialize<'de> for BitSet<Conf>{
     where
         D: serde::Deserializer<'de>
     {
+        use serde::de::Error;
+        
         if deserializer.is_human_readable() {
-            use base64::{read::DecoderReader, engine::general_purpose::STANDARD};
-            
-            let s: &str = <&str>::deserialize(deserializer)?;
-            let mut decoder = DecoderReader::new(Cursor::new(s), &STANDARD);
-            
-            BitSet::deserialize(&mut decoder).map_err(serde::de::Error::custom)
+            struct Visitor<Conf>(PhantomData<Conf>);
+            impl<'de, Conf: Config> serde::de::Visitor<'de> for Visitor<Conf> {
+                type Value = BitSet<Conf>;
+
+                fn expecting(&self, formatter: &mut Formatter) -> fmt::Result {
+                    formatter.write_str("a string")
+                }
+
+                fn visit_str<E: Error>(self, v: &str) -> Result<Self::Value, E> {
+                    use base64::{read::DecoderReader, engine::general_purpose::STANDARD};
+                    let mut decoder = DecoderReader::new(Cursor::new(v), &STANDARD);
+                    BitSet::deserialize(&mut decoder).map_err(Error::custom)
+                }
+            }
+            deserializer.deserialize_str(Visitor(PhantomData))
         } else {
             struct Visitor<Conf>(PhantomData<Conf>);
             impl<'de, Conf: Config> serde::de::Visitor<'de> for Visitor<Conf> {
                 type Value = BitSet<Conf>;
             
-                fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+                fn expecting(&self, formatter: &mut Formatter) -> fmt::Result {
                     formatter.write_str("a byte slice")
                 }
 
-                fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
-                where
-                    E: serde::de::Error,
-                {
-                    BitSet::deserialize(&mut Cursor::new(v)).map_err(serde::de::Error::custom)
-                }
-
-                // Not in use now - bincode does not support deserialize_any
-                /// This is a fallback implementation for serializers that 
-                /// lie in is_human_readable().
-                fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
-                where
-                    A: SeqAccess<'de>,
-                {
-                    let mut v: Vec<u8> = 
-                        if let Some(len) = seq.size_hint() {
-                            Vec::with_capacity(len)
-                        } else {
-                            Vec::new()    
-                        };
-                    
-                    while let Some(byte) = seq.next_element::<u8>()? {
-                        v.push(byte);
-                    }
-                    
-                    BitSet::deserialize(&mut Cursor::new(v)).map_err(serde::de::Error::custom)
+                fn visit_bytes<E: Error>(self, v: &[u8]) -> Result<Self::Value, E> {
+                    BitSet::deserialize(&mut Cursor::new(v)).map_err(Error::custom)
                 }
             }            
             deserializer.deserialize_bytes(Visitor(PhantomData))
@@ -103,6 +91,7 @@ impl<'de, Conf: Config> Deserialize<'de> for BitSet<Conf>{
 
 #[cfg(test)]
 mod tests {
+    use std::io::Seek;
     use itertools::assert_equal;
     use crate::config;
     use super::*;
@@ -141,4 +130,17 @@ mod tests {
         assert_eq!(bitset, deserialized_bitset);
         assert_equal(bitset.iter(), deserialized_bitset.iter());    // check by iter too.
     }
+    
+    #[test]
+    fn serde_json_w_file() -> anyhow::Result<()> {
+        type BitSet = crate::BitSet<config::_64bit>;
+        let set = BitSet::from_iter(0..260_000usize);
+        
+        let mut file = tempfile::tempfile()?;
+        serde_json::to_writer(&mut file, &set)?;
+        
+        file.rewind()?;
+        let _s: BitSet = serde_json::from_reader(file)?;
+        Ok(())
+    }    
 }
\ No newline at end of file