diff --git a/CHANGELOG.md b/CHANGELOG.md
index c03a5106..24034e1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,12 +1,13 @@
 Rhai Release Notes
 ==================
 
-Version 1.5.0
+Version 1.4.1
 =============
 
 Bug fixes
 ---------
 
+* Expressions such as `x = x + 1` no longer panics.
 * Padding arrays with another array via `pad` no longer loops indefinitely.
 * `chop` for arrays and BLOB's now works properly.
 * `set_bit` for bit-flags with negative index now works correctly.
diff --git a/src/ast/stmt.rs b/src/ast/stmt.rs
index a4580c1b..136356a1 100644
--- a/src/ast/stmt.rs
+++ b/src/ast/stmt.rs
@@ -45,7 +45,7 @@ impl OpAssignment<'_> {
     #[must_use]
     pub fn new_from_token(op: Token) -> Self {
         let op_raw = op
-            .map_op_assignment()
+            .get_base_op_from_assignment()
             .expect("op-assignment operator")
             .literal_syntax();
         Self {
@@ -54,6 +54,26 @@ impl OpAssignment<'_> {
             op: op.literal_syntax(),
         }
     }
+    /// Create a new [`OpAssignment`] from a base operator.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the name is not an operator that can be converted into an op-operator.
+    #[must_use]
+    #[inline(always)]
+    pub fn new_from_base(name: &str) -> Self {
+        Self::new_from_base_token(Token::lookup_from_syntax(name).expect("operator"))
+    }
+    /// Convert a [`Token`] into a new [`OpAssignment`].
+    ///
+    /// # Panics
+    ///
+    /// Panics if the token is cannot be converted into an op-assignment operator.
+    #[inline(always)]
+    #[must_use]
+    pub fn new_from_base_token(op: Token) -> Self {
+        Self::new_from_token(op.convert_to_op_assignment().expect("operator"))
+    }
 }
 
 /// _(internals)_ A scoped block of statements.
diff --git a/src/optimizer.rs b/src/optimizer.rs
index 0244f8cf..7bfe8bbf 100644
--- a/src/optimizer.rs
+++ b/src/optimizer.rs
@@ -423,7 +423,7 @@ fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: b
             match x.2 {
                 Expr::FnCall(ref mut x2, _) => {
                     state.set_dirty();
-                    x.1 = Some(OpAssignment::new(&x2.name));
+                    x.1 = Some(OpAssignment::new_from_base(&x2.name));
 
                     let value = mem::take(&mut x2.args[1]);
 
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index e82997ac..b23c630e 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -636,7 +636,7 @@ impl Token {
 
     /// Get the corresponding operator of the token if it is an op-assignment operator.
     #[must_use]
-    pub const fn map_op_assignment(&self) -> Option<Self> {
+    pub const fn get_base_op_from_assignment(&self) -> Option<Self> {
         Some(match self {
             Self::PlusAssign => Self::Plus,
             Self::MinusAssign => Self::Minus,
@@ -675,7 +675,7 @@ impl Token {
 
     /// Get the corresponding op-assignment operator of the token.
     #[must_use]
-    pub const fn make_op_assignment(&self) -> Option<Self> {
+    pub const fn convert_to_op_assignment(&self) -> Option<Self> {
         Some(match self {
             Self::Plus => Self::PlusAssign,
             Self::Minus => Self::MinusAssign,
diff --git a/tests/ops.rs b/tests/ops.rs
index d50bf517..df5be33c 100644
--- a/tests/ops.rs
+++ b/tests/ops.rs
@@ -6,6 +6,11 @@ fn test_ops() -> Result<(), Box<EvalAltResult>> {
 
     assert_eq!(engine.eval::<INT>("60 + 5")?, 65);
     assert_eq!(engine.eval::<INT>("(1 + 2) * (6 - 4) / 2")?, 3);
+    assert_eq!(engine.eval::<INT>("let x = 41; x = x + 1; x")?, 42);
+    assert_eq!(
+        engine.eval::<String>(r#"let s = "hello"; s = s + 42; s"#)?,
+        "hello42"
+    );
 
     Ok(())
 }