diff --git a/Cargo.toml b/Cargo.toml
index 2aa8992a2..41d54c1b8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,14 +12,14 @@ repository = "https://japaric.github.io/serde-json-core/serde_json_core"
 version = "0.0.1"
 
 [dependencies]
-heapless = "0.4.0"
+heapless = "0.5.1"
 
 [dependencies.serde]
 default-features = false
-version = "1.0.80"
+version = "1.0.102"
 
 [dev-dependencies]
-serde_derive = "1.0.80"
+serde_derive = "1.0.102"
 
 [features]
-std = ["serde/std"]
\ No newline at end of file
+std = ["serde/std"]
diff --git a/src/de/enum_.rs b/src/de/enum_.rs
index dcc983854..7e516878e 100644
--- a/src/de/enum_.rs
+++ b/src/de/enum_.rs
@@ -2,10 +2,7 @@ use serde::de;
 
 use crate::de::{Deserializer, Error, Result};
 
-pub(crate) struct UnitVariantAccess<'a, 'b>
-where
-    'b: 'a,
-{
+pub(crate) struct UnitVariantAccess<'a, 'b> {
     de: &'a mut Deserializer<'b>,
 }
 
diff --git a/src/de/map.rs b/src/de/map.rs
index fc0e77b39..5af92ec17 100644
--- a/src/de/map.rs
+++ b/src/de/map.rs
@@ -2,10 +2,7 @@ use serde::de::{self, Visitor};
 
 use crate::de::{Deserializer, Error};
 
-pub struct MapAccess<'a, 'b>
-where
-    'b: 'a,
-{
+pub struct MapAccess<'a, 'b> {
     de: &'a mut Deserializer<'b>,
     first: bool,
 }
@@ -60,10 +57,7 @@ impl<'a, 'de> de::MapAccess<'de> for MapAccess<'a, 'de> {
     }
 }
 
-struct MapKey<'a, 'b>
-where
-    'b: 'a,
-{
+struct MapKey<'a, 'b> {
     de: &'a mut Deserializer<'b>,
 }
 
diff --git a/src/de/seq.rs b/src/de/seq.rs
index b809dd165..f3dbbdca3 100644
--- a/src/de/seq.rs
+++ b/src/de/seq.rs
@@ -2,10 +2,7 @@ use serde::de;
 
 use crate::de::{Deserializer, Error, Result};
 
-pub(crate) struct SeqAccess<'a, 'b>
-where
-    'b: 'a,
-{
+pub(crate) struct SeqAccess<'a, 'b> {
     first: bool,
     de: &'a mut Deserializer<'b>,
 }
diff --git a/src/lib.rs b/src/lib.rs
index 41df0c9c2..3d068ab1d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -57,7 +57,7 @@
 #![deny(rust_2018_compatibility)]
 #![deny(rust_2018_idioms)]
 #![deny(warnings)]
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 pub mod de;
 pub mod ser;
diff --git a/src/ser/mod.rs b/src/ser/mod.rs
index f7d06a462..ef892e032 100644
--- a/src/ser/mod.rs
+++ b/src/ser/mod.rs
@@ -69,12 +69,13 @@ where
 // which take 200+ bytes of ROM / Flash
 macro_rules! serialize_unsigned {
     ($self:ident, $N:expr, $v:expr) => {{
-        let mut buf: [u8; $N] = unsafe { mem::uninitialized() };
+        let mut buf: [mem::MaybeUninit<u8>; $N] =
+            unsafe { mem::MaybeUninit::uninit().assume_init() };
 
         let mut v = $v;
         let mut i = $N - 1;
         loop {
-            buf[i] = (v % 10) as u8 + b'0';
+            buf[i] = mem::MaybeUninit::new((v % 10) as u8 + b'0');
             v /= 10;
 
             if v == 0 {
@@ -84,7 +85,9 @@ macro_rules! serialize_unsigned {
             }
         }
 
-        $self.buf.extend_from_slice(&buf[i..])?;
+        $self
+            .buf
+            .extend_from_slice(unsafe { mem::transmute::<_, &[u8]>(&buf[i..]) })?;
         Ok(())
     }};
 }
@@ -100,10 +103,11 @@ macro_rules! serialize_signed {
             (false, v as $uxx)
         };
 
-        let mut buf: [u8; $N] = unsafe { mem::uninitialized() };
+        let mut buf: [mem::MaybeUninit<u8>; $N] =
+            unsafe { mem::MaybeUninit::uninit().assume_init() };
         let mut i = $N - 1;
         loop {
-            buf[i] = (v % 10) as u8 + b'0';
+            buf[i] = mem::MaybeUninit::new((v % 10) as u8 + b'0');
             v /= 10;
 
             i -= 1;
@@ -114,11 +118,13 @@ macro_rules! serialize_signed {
         }
 
         if signed {
-            buf[i] = b'-';
+            buf[i] = mem::MaybeUninit::new(b'-');
         } else {
             i += 1;
         }
-        $self.buf.extend_from_slice(&buf[i..])?;
+        $self
+            .buf
+            .extend_from_slice(unsafe { mem::transmute::<_, &[u8]>(&buf[i..]) })?;
         Ok(())
     }};
 }