diff --git a/Makefile b/Makefile
index 8355918c5..7ad96636e 100644
--- a/Makefile
+++ b/Makefile
@@ -486,6 +486,9 @@ test-packages:
 
 test-js: test-js-api test-js-wasi
 
+test-js-core:
+	cd lib/api && wasm-pack test --node -- --no-default-features --features js,core,wasm-types-polyfill,wat
+
 test-js-api:
 	cd lib/api && wasm-pack test --node -- --no-default-features --features js-default,wat
 
diff --git a/lib/api/src/js/error.rs b/lib/api/src/js/error.rs
index f334b4a1c..0bd656af7 100644
--- a/lib/api/src/js/error.rs
+++ b/lib/api/src/js/error.rs
@@ -2,6 +2,8 @@ use crate::js::lib::std::string::String;
 use crate::js::trap::RuntimeError;
 #[cfg(feature = "std")]
 use std::borrow::Cow;
+#[cfg(feature = "core")]
+use crate::alloc::borrow::Cow;
 #[cfg(feature = "std")]
 use thiserror::Error;
 
@@ -115,7 +117,7 @@ impl From<wasm_bindgen::JsValue> for WasmError {
 pub enum SerializeError {
     /// An IO error
     #[cfg_attr(feature = "std", error(transparent))]
-    Io(#[from] std::io::Error),
+    Io(#[cfg_attr(feature = "std", from)] std::io::Error),
     /// A generic serialization error
     #[cfg_attr(feature = "std", error("{0}"))]
     Generic(String),
@@ -124,11 +126,12 @@ pub enum SerializeError {
 /// The Deserialize error can occur when loading a
 /// compiled Module from a binary.
 /// Copied from wasmer_compiler::DeSerializeError
-#[derive(Error, Debug)]
+#[derive(Debug)]
+#[cfg_attr(feature = "std", derive(Error))]
 pub enum DeserializeError {
     /// An IO error
     #[cfg_attr(feature = "std", error(transparent))]
-    Io(#[from] std::io::Error),
+    Io(#[cfg_attr(feature = "std", from)] std::io::Error),
     /// A generic deserialization error
     #[cfg_attr(feature = "std", error("{0}"))]
     Generic(String),
diff --git a/lib/api/src/js/mod.rs b/lib/api/src/js/mod.rs
index a642e14b5..99aa2c22b 100644
--- a/lib/api/src/js/mod.rs
+++ b/lib/api/src/js/mod.rs
@@ -7,12 +7,12 @@ compile_error!(
 compile_error!("Both the `std` and `core` features are disabled. Please enable one of them.");
 
 #[cfg(feature = "core")]
-extern crate alloc;
+pub(crate) extern crate alloc;
 
 mod lib {
     #[cfg(feature = "core")]
     pub mod std {
-        pub use alloc::{borrow, boxed, str, string, sync, vec};
+        pub use crate::alloc::{borrow, boxed, str, string, sync, vec};
         pub use core::fmt;
         pub use hashbrown as collections;
     }
@@ -23,7 +23,7 @@ mod lib {
     }
 }
 
-mod error;
+pub(crate) mod error;
 mod export;
 mod exports;
 mod externals;
diff --git a/lib/api/src/js/trap.rs b/lib/api/src/js/trap.rs
index 0d5ca5318..1273851a3 100644
--- a/lib/api/src/js/trap.rs
+++ b/lib/api/src/js/trap.rs
@@ -6,6 +6,10 @@ use wasm_bindgen::convert::FromWasmAbi;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsValue;
 
+pub trait CoreError: fmt::Debug + fmt::Display + core::any::Any { }
+
+impl<T: fmt::Debug + fmt::Display + core::any::Any> CoreError for T { }
+
 /// A struct representing an aborted instruction execution, with a message
 /// indicating the cause.
 #[wasm_bindgen]
@@ -30,7 +34,10 @@ impl PartialEq for RuntimeError {
 #[derive(Debug)]
 enum RuntimeErrorSource {
     Generic(String),
+    #[cfg(feature = "std")]
     User(Box<dyn Error + Send + Sync>),
+    #[cfg(feature = "core")]
+    User(Box<dyn CoreError + Send + Sync>),
     Js(JsValue),
 }
 
@@ -74,6 +81,7 @@ impl RuntimeError {
     ///
     /// This error object can be passed through Wasm frames and later retrieved
     /// using the `downcast` method.
+    #[cfg(feature = "std")]
     pub fn user(error: Box<dyn Error + Send + Sync>) -> Self {
         match error.downcast::<Self>() {
             // The error is already a RuntimeError, we return it directly
@@ -84,6 +92,17 @@ impl RuntimeError {
         }
     }
 
+    #[cfg(feature = "core")]
+    pub fn user(error: Box<dyn CoreError + Send + Sync>) -> Self {
+        match error.downcast::<Self>() {
+            // The error is already a RuntimeError, we return it directly
+            Ok(runtime_error) => *runtime_error,
+            Err(error) => RuntimeError {
+                inner: Arc::new(RuntimeErrorSource::User(error)),
+            },
+        }
+    }
+
     /// Returns a reference the `message` stored in `Trap`.
     pub fn message(&self) -> String {
         format!("{}", self.inner)
diff --git a/lib/compiler/src/engine/trap/error.rs b/lib/compiler/src/engine/trap/error.rs
index 76ae212fb..60e033985 100644
--- a/lib/compiler/src/engine/trap/error.rs
+++ b/lib/compiler/src/engine/trap/error.rs
@@ -12,12 +12,19 @@ pub struct RuntimeError {
     inner: Arc<RuntimeErrorInner>,
 }
 
+pub trait CoreError: fmt::Debug + fmt::Display + core::any::Any { }
+
+impl<T: fmt::Debug + fmt::Display + core::any::Any> CoreError for T { }
+
 /// The source of the `RuntimeError`.
 #[derive(Debug)]
 enum RuntimeErrorSource {
     Generic(String),
     OutOfMemory,
+    #[cfg(feature = "std")]
     User(Box<dyn Error + Send + Sync>),
+    #[cfg(feature = "core")]
+    User(Box<dyn CoreError + Send + Sync>),
     Trap(TrapCode),
 }
 
@@ -110,6 +117,7 @@ impl RuntimeError {
     ///
     /// This error object can be passed through Wasm frames and later retrieved
     /// using the `downcast` method.
+    #[cfg(feature = "std")]
     pub fn user(error: Box<dyn Error + Send + Sync>) -> Self {
         match error.downcast::<Self>() {
             // The error is already a RuntimeError, we return it directly
@@ -126,6 +134,27 @@ impl RuntimeError {
         }
     }
 
+    /// Creates a custom user Error.
+    ///
+    /// This error object can be passed through Wasm frames and later retrieved
+    /// using the `downcast` method.
+    #[cfg(feature = "core")]
+    pub fn user(error: Box<dyn CoreError + Send + Sync>) -> Self {
+        match error.downcast::<Self>() {
+            // The error is already a RuntimeError, we return it directly
+            Ok(runtime_error) => *runtime_error,
+            Err(error) => {
+                let info = FRAME_INFO.read().unwrap();
+                Self::new_with_trace(
+                    &info,
+                    None,
+                    RuntimeErrorSource::User(error),
+                    Backtrace::new_unresolved(),
+                )
+            }
+        }
+    }
+
     fn new_with_trace(
         info: &GlobalFrameInfo,
         trap_pc: Option<usize>,