diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 069f965..7bd1559 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -42,6 +42,13 @@ jobs:
       - name: Run cargo check (without dev-dependencies to catch missing feature flags)
         if: startsWith(matrix.rust, 'nightly')
         run: cargo check -Z features=dev_dep
+      - name: Add rust-src
+        if: startsWith(matrix.rust, 'nightly')
+        run: rustup component add rust-src
+# https://github.com/smol-rs/async-io/pull/144#issuecomment-1666927490
+#      - name: Check selected Tier 3 targets
+#        if: startsWith(matrix.rust, 'nightly') && matrix.os == 'ubuntu-latest'
+#        run: cargo check -Z build-std --target=riscv32imc-esp-espidf
       - run: cargo test
 
   # Copied from: https://github.com/rust-lang/stacker/pull/19/files
diff --git a/src/reactor.rs b/src/reactor.rs
index dda9f92..3e39534 100644
--- a/src/reactor.rs
+++ b/src/reactor.rs
@@ -43,6 +43,14 @@ cfg_if::cfg_if! {
     }
 }
 
+#[cfg(not(target_os = "espidf"))]
+const TIMER_QUEUE_SIZE: usize = 1000;
+
+/// ESP-IDF - being an embedded OS - does not need so many timers
+/// and this saves ~ 20K RAM which is a lot for an MCU with RAM < 400K
+#[cfg(target_os = "espidf")]
+const TIMER_QUEUE_SIZE: usize = 100;
+
 const READ: usize = 0;
 const WRITE: usize = 1;
 
@@ -98,7 +106,7 @@ impl Reactor {
                 sources: Mutex::new(Slab::new()),
                 events: Mutex::new(Vec::new()),
                 timers: Mutex::new(BTreeMap::new()),
-                timer_ops: ConcurrentQueue::bounded(1000),
+                timer_ops: ConcurrentQueue::bounded(TIMER_QUEUE_SIZE),
             }
         })
     }