diff --git a/hm-asm-web/README.md b/hm-asm-web/README.md
index 0624c27..955b4dd 100644
--- a/hm-asm-web/README.md
+++ b/hm-asm-web/README.md
@@ -5,6 +5,9 @@ two functions to javascript.
 - `simulate(code: &str, cycles: usize)`, its return value is equivalent to the one of `hm_asm_simulator::simulate::simulate`
 - `assemble(code: &str)`, its return vlaue is equivalent to the one of `hm_asm_simulator::generate::generate_binary`
 
+If either of the functions should fail they will return their Rust error as a String. In the case of a grammar based
+error, this would be a nice pest.rs error.
+
 ## Demo
 In `demo/` You'll find a demo app that compiles and simulates a simple program inside of the console.
 You can test it with
diff --git a/hm-asm-web/demo/index.js b/hm-asm-web/demo/index.js
index 2882d26..dd9409b 100644
--- a/hm-asm-web/demo/index.js
+++ b/hm-asm-web/demo/index.js
@@ -2,8 +2,13 @@ import * as wasm from "hm-asm-web";
 
 
 console.log("Welcome to hm-asm-web");
-const code = "LDA #1\nADD #3\nSTA (8)"
-console.log("Compiling:\n" + code)
+const code = "LDA #1\nADD #3\nSTA (8)";
+console.log("Compiling:\n" + code);
 console.log(wasm.assemble(code));
-console.log("Simulating for four clock cycles:\n" + code )
+console.log("Simulating for four clock cycles:\n" + code);
 console.log(wasm.simulate(code, 4));
+
+const invalid = "LDA dkfljlsdkfjsdf";
+console.log("Compiling invalid code:\n" + invalid);
+console.log(wasm.assemble(invalid));
+console.log("Hurray a nice error msg");
diff --git a/hm-asm-web/src/lib.rs b/hm-asm-web/src/lib.rs
index d865634..56f949d 100644
--- a/hm-asm-web/src/lib.rs
+++ b/hm-asm-web/src/lib.rs
@@ -9,9 +9,10 @@ use hm_asm_simulator::{
 
 #[wasm_bindgen]
 pub fn simulate(code: &str, cycles: usize) -> JsValue {
-    let instructions = parse_asm(
-        AsmParser::parse(Rule::program, &code).unwrap_or_else(|e| panic!("{}", e)),
-    );
+    let instructions = parse_asm(match AsmParser::parse(Rule::program, &code) {
+        Ok(instructions) => instructions,
+        Err(e) => return JsValue::from_str(&format!("{}", e))
+    });
     let states = hm_asm_simulator::simulate::simulate(instructions, cycles);
 
     JsValue::from_serde(&states).unwrap()
@@ -20,9 +21,12 @@ pub fn simulate(code: &str, cycles: usize) -> JsValue {
 
 #[wasm_bindgen]
 pub fn assemble(code: &str) -> JsValue {
-    let instructions = parse_asm(
-        AsmParser::parse(Rule::program, &code).unwrap_or_else(|e| panic!("{}", e)),
-    );
+    let instructions = parse_asm(match AsmParser::parse(Rule::program, &code) {
+        Ok(instructions) => instructions,
+        Err(e) => return JsValue::from_str(&format!("{}", e))
+    });
+
+
     let binary = generate_binary(instructions);
     JsValue::from_serde(&binary).unwrap()
 }