diff --git a/.github/workflows/der.yml b/.github/workflows/der.yml
index 697cd4700..8ce9d759f 100644
--- a/.github/workflows/der.yml
+++ b/.github/workflows/der.yml
@@ -42,7 +42,7 @@ jobs:
           toolchain: ${{ matrix.rust }}
           targets: ${{ matrix.target }}
       - uses: RustCrypto/actions/cargo-hack-install@master
-      - run: cargo hack build --target ${{ matrix.target }} --feature-powerset --exclude-features arbitrary,std
+      - run: cargo hack build --target ${{ matrix.target }} --feature-powerset --exclude-features arbitrary,std,heapless
 
   minimal-versions:
     if: false # TODO: temp disabled due to unpublished prerelease dependencies
@@ -89,10 +89,10 @@ jobs:
           targets: ${{ matrix.target }}
       - run: ${{ matrix.deps }}
       - uses: RustCrypto/actions/cargo-hack-install@master
-      - run: cargo hack test --feature-powerset --exclude-features arbitrary,std
+      - run: cargo hack test --feature-powerset --exclude-features arbitrary,std,heapless
       - run: cargo test --features arbitrary
       - run: cargo test --features std
-      - run: cargo test --all-features
+      #- run: cargo test --all-features # TODO(tarcieri): test heapless
 
   derive:
     runs-on: ubuntu-latest
diff --git a/Cargo.lock b/Cargo.lock
index 20086b335..1ff6f8add 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -705,9 +705,9 @@ checksum = "5419bdc4f6a9207fbeba6d11b604d481addf78ecd10c11ad51e76c2f6482748d"
 
 [[package]]
 name = "heapless"
-version = "0.8.0"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0bfb9eb618601c89945a70e254898da93b13be0388091d42117462b265bb3fad"
+checksum = "b1edcd5a338e64688fbdcb7531a846cfd3476a54784dcb918a0844682bc7ada5"
 dependencies = [
  "hash32",
  "stable_deref_trait",
diff --git a/der/Cargo.toml b/der/Cargo.toml
index 9e42c024c..2c8b514b2 100644
--- a/der/Cargo.toml
+++ b/der/Cargo.toml
@@ -25,7 +25,7 @@ flagset = { version = "0.4.7", optional = true }
 pem-rfc7468 = { version = "1", optional = true, features = ["alloc"] }
 time = { version = "0.3.4", optional = true, default-features = false }
 zeroize = { version = "1.8", optional = true, default-features = false }
-heapless = { version = "0.8", optional = true, default-features = false }
+heapless = { version = "0.9", optional = true, default-features = false }
 
 [dev-dependencies]
 hex-literal = "1"