diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 94069895..f0c81c64 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,7 +22,7 @@ jobs:
 
         include:
           # Test MSRV
-          - rust: 1.70.0  # keep in sync with manifest rust-version
+          - rust: 1.87.0  # keep in sync with manifest rust-version
             TARGET: x86_64-unknown-linux-gnu
 
           # Test nightly but don't fail
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b4e416c..d00c3e30 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 ### Breaking
-- MSRV is now `1.70.0`.
+- MSRV is now `1.87.0`.
 
 ## [v0.6.0] - 2024-08-07
 
diff --git a/Cargo.toml b/Cargo.toml
index c8cafd08..0887f79b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,7 +8,7 @@ categories = ["parsing", "no-std", "no-std::no-alloc", "embedded", "web-programm
 description = "serde-json for no_std programs"
 documentation = "https://docs.rs/serde-json-core"
 edition = "2018"
-rust-version = "1.70.0"  # keep in sync with ci, src/lib.rs, and README
+rust-version = "1.87.0"  # keep in sync with ci, src/lib.rs, and README
 keywords = ["serde", "json"]
 license = "MIT OR Apache-2.0"
 name = "serde-json-core"
@@ -20,7 +20,7 @@ version = "0.6.0"
 ryu = "1.0.5"
 
 [dependencies.heapless]
-version = "0.8"
+version = "0.9.1"
 features = ["serde"]
 optional = true
 
@@ -30,7 +30,7 @@ features = ["derive"]
 version = "1.0.100"
 
 [dependencies.defmt]
-version = "0.3"
+version = "1.0.1"
 optional = true
 
 [dev-dependencies]
@@ -40,4 +40,4 @@ serde_derive = "1.0.100"
 default = ["heapless"]
 custom-error-messages = ["heapless"]
 std = ["serde/std"]
-defmt = ["dep:defmt", "heapless?/defmt-03"]
+defmt = ["dep:defmt", "heapless?/defmt"]
diff --git a/README.md b/README.md
index b1640796..55c01453 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ This project is developed and maintained by the [rust-embedded-community].
 
 ## Minimum Supported Rust Version (MSRV)
 
-This crate is guaranteed to compile on stable Rust 1.70.0 and up. It *might*
+This crate is guaranteed to compile on stable Rust 1.87.0 and up. It *might*
 compile with older versions but that may change in any new patch release.
 
 ## License
diff --git a/src/ser/mod.rs b/src/ser/mod.rs
index 273072f2..b45c5695 100644
--- a/src/ser/mod.rs
+++ b/src/ser/mod.rs
@@ -42,6 +42,13 @@ impl From<u8> for Error {
     }
 }
 
+#[cfg(feature = "heapless")]
+impl From<heapless::CapacityError> for Error {
+    fn from(_: heapless::CapacityError) -> Self {
+        Error::BufferFull
+    }
+}
+
 impl serde::ser::StdError for Error {}
 
 impl fmt::Display for Error {