diff --git a/heterogeneous/src/lib.rs b/heterogeneous/src/lib.rs
index a4f0ec570e..3288bfe012 100644
--- a/heterogeneous/src/lib.rs
+++ b/heterogeneous/src/lib.rs
@@ -8,7 +8,7 @@ use core::{
 };
 
 use bare_metal::Nr;
-use rtfm::Monotonic;
+use rtfm::{Monotonic, MultiCore};
 
 // both cores have the exact same interrupts
 pub use Interrupt_0 as Interrupt_1;
@@ -21,7 +21,7 @@ pub fn xpend(_core: u8, _interrupt: impl Nr) {}
 /// Fake monotonic timer
 pub struct MT;
 
-unsafe impl Monotonic for MT {
+impl Monotonic for MT {
     type Instant = Instant;
 
     fn ratio() -> u32 {
@@ -41,6 +41,8 @@ unsafe impl Monotonic for MT {
     }
 }
 
+impl MultiCore for MT {}
+
 #[derive(Clone, Copy, Eq, PartialEq)]
 pub struct Instant(i32);
 
diff --git a/homogeneous/src/lib.rs b/homogeneous/src/lib.rs
index a4f0ec570e..3288bfe012 100644
--- a/homogeneous/src/lib.rs
+++ b/homogeneous/src/lib.rs
@@ -8,7 +8,7 @@ use core::{
 };
 
 use bare_metal::Nr;
-use rtfm::Monotonic;
+use rtfm::{Monotonic, MultiCore};
 
 // both cores have the exact same interrupts
 pub use Interrupt_0 as Interrupt_1;
@@ -21,7 +21,7 @@ pub fn xpend(_core: u8, _interrupt: impl Nr) {}
 /// Fake monotonic timer
 pub struct MT;
 
-unsafe impl Monotonic for MT {
+impl Monotonic for MT {
     type Instant = Instant;
 
     fn ratio() -> u32 {
@@ -41,6 +41,8 @@ unsafe impl Monotonic for MT {
     }
 }
 
+impl MultiCore for MT {}
+
 #[derive(Clone, Copy, Eq, PartialEq)]
 pub struct Instant(i32);
 
diff --git a/macros/src/codegen.rs b/macros/src/codegen.rs
index 927662606c..a3515994bf 100644
--- a/macros/src/codegen.rs
+++ b/macros/src/codegen.rs
@@ -32,7 +32,7 @@ pub fn app(app: &App, analysis: &Analysis, extra: &Extra) -> TokenStream2 {
 
     // generate a `main` function for each core
     for core in 0..app.args.cores {
-        let assertion_stmts = assertions::codegen(core, analysis);
+        let assertion_stmts = assertions::codegen(core, analysis, extra);
 
         let (const_app_pre_init, pre_init_stmts) = pre_init::codegen(core, &app, analysis, extra);
 
diff --git a/macros/src/codegen/assertions.rs b/macros/src/codegen/assertions.rs
index 95268a2cf4..4a77352f57 100644
--- a/macros/src/codegen/assertions.rs
+++ b/macros/src/codegen/assertions.rs
@@ -1,10 +1,10 @@
 use proc_macro2::TokenStream as TokenStream2;
 use quote::quote;
 
-use crate::analyze::Analysis;
+use crate::{analyze::Analysis, check::Extra};
 
 /// Generates compile-time assertions that check that types implement the `Send` / `Sync` traits
-pub fn codegen(core: u8, analysis: &Analysis) -> Vec<TokenStream2> {
+pub fn codegen(core: u8, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream2> {
     let mut stmts = vec![];
 
     // we don't generate *all* assertions on all cores because the user could conditionally import a
@@ -22,5 +22,12 @@ pub fn codegen(core: u8, analysis: &Analysis) -> Vec<TokenStream2> {
         }
     }
 
+    // if the `schedule` API is used in more than one core then we need to check that the
+    // `monotonic` timer can be used in multi-core context
+    if analysis.timer_queues.len() > 1 && analysis.timer_queues.contains_key(&core) {
+        let monotonic = extra.monotonic();
+        stmts.push(quote!(rtfm::export::assert_multicore::<#monotonic>();));
+    }
+
     stmts
 }
diff --git a/src/cyccnt.rs b/src/cyccnt.rs
index a2b216c179..468aa712b6 100644
--- a/src/cyccnt.rs
+++ b/src/cyccnt.rs
@@ -116,6 +116,11 @@ pub struct Duration {
 }
 
 impl Duration {
+    /// Creates a new `Duration` from the specified number of clock cycles
+    pub fn from_cycles(cycles: u32) -> Self {
+        Duration { inner: cycles }
+    }
+
     /// Returns the total number of clock cycles contained by this `Duration`
     pub fn as_cycles(&self) -> u32 {
         self.inner
@@ -181,7 +186,7 @@ impl U32Ext for u32 {
 pub struct CYCCNT;
 
 #[cfg(not(feature = "heterogeneous"))]
-unsafe impl crate::Monotonic for CYCCNT {
+impl crate::Monotonic for CYCCNT {
     type Instant = Instant;
 
     fn ratio() -> u32 {
diff --git a/src/export.rs b/src/export.rs
index 7646e3c504..572068ce22 100644
--- a/src/export.rs
+++ b/src/export.rs
@@ -108,6 +108,13 @@ where
 {
 }
 
+#[inline(always)]
+pub fn assert_multicore<T>()
+where
+    T: super::MultiCore,
+{
+}
+
 #[cfg(armv7m)]
 #[inline(always)]
 pub unsafe fn lock<T, R>(
diff --git a/src/lib.rs b/src/lib.rs
index acb3a63db3..decd2da1b7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -117,7 +117,7 @@ impl From<cortex_m::Peripherals> for Peripherals {
 }
 
 /// A monotonic clock / counter
-pub unsafe trait Monotonic {
+pub trait Monotonic {
     /// A measurement of this clock
     type Instant: Copy + Ord + Sub;
 
@@ -134,6 +134,9 @@ pub unsafe trait Monotonic {
     fn zero() -> Self::Instant;
 }
 
+/// A marker trait that indicates that it is correct to use this type in multi-core context
+pub trait MultiCore {}
+
 /// Sets the given `interrupt` as pending
 ///
 /// This is a convenience function around