diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index fe1da43..2c9c56b 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -80,7 +80,7 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --no-default-features --features ${{ matrix.feature }}
+          args: --no-default-features --features "std, ${{ matrix.feature }}"
 
   no_std_features:
     name: Test Individual Features NoStd
@@ -106,7 +106,7 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --no-default-features --features "no_std, ${{ matrix.feature }}"
+          args: --no-default-features --features "${{ matrix.feature }}"
 
   test:
     name: Test
@@ -153,4 +153,4 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: test 
-          args: --features "no_std"
+          args: --no-default-features --features "binary, json, ron, toml"
diff --git a/Cargo.toml b/Cargo.toml
index ff100ce..98e79c2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,12 +22,12 @@ edition = "2018"
 repository = "https://github.com/not-fl3/nanoserde"
 
 [features]
-default = ["json", "binary", "ron", "toml"]
+default = ["json", "binary", "ron", "toml", "std"]
 json = ["dep:nanoserde-derive", "nanoserde-derive/json"]
 binary = ["dep:nanoserde-derive", "nanoserde-derive/binary"]
 ron = ["dep:nanoserde-derive", "nanoserde-derive/ron"]
 toml = []
-no_std = []
+std = []
 
 [dependencies]
 nanoserde-derive = { path = "derive", version = "=0.2.0", optional = true }
diff --git a/derive/Cargo.toml b/derive/Cargo.toml
index ceff924..ea32cb6 100644
--- a/derive/Cargo.toml
+++ b/derive/Cargo.toml
@@ -14,4 +14,3 @@ default = []
 json = []
 binary = []
 ron = []
-no_std = []
diff --git a/derive/src/lib.rs b/derive/src/lib.rs
index c8a5e79..6863d71 100644
--- a/derive/src/lib.rs
+++ b/derive/src/lib.rs
@@ -1,4 +1,4 @@
-#![cfg_attr(feature = "no_std", no_std)]
+#![cfg(no_std)]
 
 extern crate alloc;
 extern crate proc_macro;
diff --git a/derive/src/parse.rs b/derive/src/parse.rs
index 1122733..2c08164 100644
--- a/derive/src/parse.rs
+++ b/derive/src/parse.rs
@@ -4,10 +4,12 @@
 //! https://docs.rs/syn/0.15.44/syn/enum.Type.html
 //! https://ziglang.org/documentation/0.5.0/#toc-typeInfo
 
+use alloc::collections::BTreeSet;
 use core::iter::Peekable;
-use std::collections::HashSet;
-use std::num::IntErrorKind;
+use core::num::IntErrorKind;
 
+use alloc::borrow::ToOwned;
+use alloc::boxed::Box;
 use alloc::string::{String, ToString};
 use alloc::vec::Vec;
 use alloc::{format, vec};
@@ -16,6 +18,7 @@ use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
 
 #[derive(Debug, Clone)]
 pub struct Attribute {
+    #[allow(unused)]
     pub name: String,
     pub tokens: Vec<String>,
 }
@@ -37,6 +40,7 @@ pub struct Lifetime {
 #[derive(Debug, Clone)]
 pub struct Field {
     pub attributes: Vec<Attribute>,
+    #[allow(unused)]
     pub vis: Visibility,
     pub field_name: Option<String>,
     pub ty: Type,
@@ -1079,14 +1083,14 @@ fn next_attribute<T: Iterator<Item = TokenTree>>(
             (true, _) => {
                 attrs.push(Attribute {
                     name: name.clone(),
-                    tokens: std::mem::take(&mut attr_tokens),
+                    tokens: core::mem::take(&mut attr_tokens),
                 });
                 break;
             }
             (false, Some(",")) => {
                 attrs.push(Attribute {
                     name: name.clone(),
-                    tokens: std::mem::take(&mut attr_tokens),
+                    tokens: core::mem::take(&mut attr_tokens),
                 });
                 continue;
             }
@@ -1105,14 +1109,14 @@ fn next_attribute<T: Iterator<Item = TokenTree>>(
             (true, _) => {
                 attrs.push(Attribute {
                     name: name.clone(),
-                    tokens: std::mem::take(&mut attr_tokens),
+                    tokens: core::mem::take(&mut attr_tokens),
                 });
                 break;
             }
             (false, true) => {
                 attrs.push(Attribute {
                     name: name.clone(),
-                    tokens: std::mem::take(&mut attr_tokens),
+                    tokens: core::mem::take(&mut attr_tokens),
                 });
             }
             _ => {}
@@ -1402,7 +1406,7 @@ fn next_generic<T: Iterator<Item = TokenTree> + Clone>(
 
 fn get_all_bounds<T: Iterator<Item = TokenTree> + Clone>(source: &mut Peekable<T>) -> Vec<Generic> {
     let mut ret = Vec::new();
-    let mut already = HashSet::new();
+    let mut already = BTreeSet::new();
     if source.peek().map_or(false, |x| x.to_string() == "<") {
         source.next();
     } else {
diff --git a/derive/src/shared.rs b/derive/src/shared.rs
index 110f814..735bf75 100644
--- a/derive/src/shared.rs
+++ b/derive/src/shared.rs
@@ -1,4 +1,8 @@
-use alloc::string::String;
+use alloc::{
+    format,
+    string::{String, ToString},
+    vec::Vec,
+};
 
 #[cfg(any(feature = "binary", feature = "json"))]
 use crate::parse::{Enum, Struct};
diff --git a/src/lib.rs b/src/lib.rs
index 8384509..98c2778 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,11 +15,7 @@
 //! `nanoserde` supports some serialization customisation with `#[nserde()]` attributes.
 //! For `#[nserde(..)]` supported attributes for each format check [Features support matrix](https://github.com/not-fl3/nanoserde#features-support-matrix)
 
-#![cfg_attr(feature = "no_std", no_std)]
-// Possibly stable in 1.65.
-// See: https://github.com/rust-lang/rust/pull/99917
-// and https://github.com/rust-lang/rust/issues/103765
-#![cfg_attr(feature = "no_std", feature(error_in_core))]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;
 
diff --git a/src/serde_bin.rs b/src/serde_bin.rs
index 66c7fc1..c99e858 100644
--- a/src/serde_bin.rs
+++ b/src/serde_bin.rs
@@ -77,12 +77,8 @@ impl core::fmt::Display for DeBinErr {
     }
 }
 
-#[cfg(feature = "no_std")]
 impl core::error::Error for DeBinErr {}
 
-#[cfg(not(feature = "no_std"))]
-impl std::error::Error for DeBinErr {}
-
 macro_rules! impl_ser_de_bin_for {
     ($ty:ident) => {
         impl SerBin for $ty {
@@ -287,7 +283,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> SerBin for std::collections::HashSet<T>
 where
     T: SerBin,
@@ -301,7 +297,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> DeBin for std::collections::HashSet<T>
 where
     T: DeBin + core::hash::Hash + Eq,
@@ -529,7 +525,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> SerBin for std::collections::HashMap<K, V>
 where
     K: SerBin,
@@ -545,7 +541,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> DeBin for std::collections::HashMap<K, V>
 where
     K: DeBin + core::cmp::Eq + core::hash::Hash,
diff --git a/src/serde_json.rs b/src/serde_json.rs
index 47ceef0..a10c63e 100644
--- a/src/serde_json.rs
+++ b/src/serde_json.rs
@@ -160,12 +160,8 @@ impl core::fmt::Display for DeJsonErr {
     }
 }
 
-#[cfg(feature = "no_std")]
 impl core::error::Error for DeJsonErr {}
 
-#[cfg(not(feature = "no_std"))]
-impl std::error::Error for DeJsonErr {}
-
 impl DeJsonState {
     pub fn next(&mut self, i: &mut Chars) {
         if let Some(c) = i.next() {
@@ -878,7 +874,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> SerJson for std::collections::HashSet<T>
 where
     T: SerJson,
@@ -899,7 +895,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> DeJson for std::collections::HashSet<T>
 where
     T: DeJson + core::hash::Hash + Eq,
@@ -1172,7 +1168,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> SerJson for std::collections::HashMap<K, V>
 where
     K: SerJson,
@@ -1197,7 +1193,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> DeJson for std::collections::HashMap<K, V>
 where
     K: DeJson + Eq + core::hash::Hash,
diff --git a/src/serde_ron.rs b/src/serde_ron.rs
index ce8b954..f9b8677 100644
--- a/src/serde_ron.rs
+++ b/src/serde_ron.rs
@@ -157,12 +157,8 @@ impl core::fmt::Display for DeRonErr {
     }
 }
 
-#[cfg(feature = "no_std")]
 impl core::error::Error for DeRonErr {}
 
-#[cfg(not(feature = "no_std"))]
-impl std::error::Error for DeRonErr {}
-
 impl DeRonState {
     pub fn next(&mut self, i: &mut Chars) {
         if let Some(c) = i.next() {
@@ -876,7 +872,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> SerRon for std::collections::HashSet<T>
 where
     T: SerRon,
@@ -897,7 +893,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<T> DeRon for std::collections::HashSet<T>
 where
     T: DeRon + core::hash::Hash + Eq,
@@ -1184,7 +1180,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> SerRon for std::collections::HashMap<K, V>
 where
     K: SerRon,
@@ -1204,7 +1200,7 @@ where
     }
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 impl<K, V> DeRon for std::collections::HashMap<K, V>
 where
     K: DeRon + Eq + core::hash::Hash,
diff --git a/src/toml.rs b/src/toml.rs
index 3073e02..7d1fad6 100644
--- a/src/toml.rs
+++ b/src/toml.rs
@@ -249,12 +249,8 @@ impl Out {
     }
 }
 
-#[cfg(feature = "no_std")]
 impl core::error::Error for TomlErr {}
 
-#[cfg(not(feature = "no_std"))]
-impl std::error::Error for TomlErr {}
-
 impl TomlParser {
     /// Parse a TOML string.
     pub fn parse(data: &str) -> Result<BTreeMap<String, Toml>, TomlErr> {
diff --git a/tests/json.rs b/tests/json.rs
index 5aa14d1..33a3228 100644
--- a/tests/json.rs
+++ b/tests/json.rs
@@ -6,7 +6,7 @@ use std::{
     sync::atomic::AtomicBool,
 };
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 use std::collections::HashMap;
 
 #[test]
@@ -69,6 +69,7 @@ fn de_multiline_comment() {
 fn de_illegal_inline_comment() {
     #[derive(DeJson)]
     pub struct Test {
+        #[allow(unused)]
         pub a: f32,
     }
 
@@ -92,6 +93,7 @@ fn de_illegal_inline_comment() {
 fn de_illegal_multiline_comment() {
     #[derive(DeJson)]
     pub struct Test {
+        #[allow(unused)]
         pub a: f32,
     }
 
@@ -467,7 +469,7 @@ fn path_type() {
     assert_eq!(bar.d, Some(vec![vec![1, 2], vec![3, 4]]));
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 #[test]
 fn hashmaps() {
     #[derive(DeJson)]
diff --git a/tests/ron.rs b/tests/ron.rs
index df8395e..5b7679e 100644
--- a/tests/ron.rs
+++ b/tests/ron.rs
@@ -6,7 +6,7 @@ use std::{
     sync::atomic::AtomicBool,
 };
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 use std::collections::HashMap;
 
 #[test]
@@ -263,7 +263,7 @@ fn path_type() {
     assert_eq!(bar.d, Some(vec![vec![1, 2], vec![3, 4]]));
 }
 
-#[cfg(not(feature = "no_std"))]
+#[cfg(feature = "std")]
 #[test]
 fn hashmaps() {
     #[derive(DeRon)]