diff --git a/releasenotes.md b/releasenotes.md
index deb0074c0..82fd7372b 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -7,6 +7,7 @@
 ### Fixes
 - Compiler assert with var x @noinit = 0 #2452
 - Confusing error message when type has [] overloaded but not []= #2453
+- $defined(x[0] = val) causes an error instead of returning false when a type does not have []= defined #2454
 
 ### Stdlib changes
 
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index 502258653..21f10d3ee 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -3909,7 +3909,7 @@ SKIP:
 	return true;
 }
 
-static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr *expr, bool check_valid)
+static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr *expr, bool *failed_ref)
 {
 	// Evaluate the expression to index.
 	Expr *subscripted = exprptr(expr->subscript_expr.expr);
@@ -3948,12 +3948,11 @@ static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr
 	Decl *overload;
 	Type *subscript_type;
 	int64_t index_value;
-	if (!sema_expr_resolve_subscript_index(context, expr, subscripted, index, &current_type, &current_expr, &subscript_type, &overload, &index_value, false, OVERLOAD_ELEMENT_SET, check_valid))
+	if (!sema_expr_resolve_subscript_index(context, expr, subscripted, index, &current_type, &current_expr, &subscript_type, &overload, &index_value, false, OVERLOAD_ELEMENT_SET, failed_ref != NULL))
 	{
-		if (check_valid && expr_ok(index))
+		if (failed_ref && expr_ok(index))
 		{
-			expr_poison(expr);
-			return true;
+			*failed_ref = true;
 		}
 		return false;
 	}
@@ -3963,7 +3962,7 @@ static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr
 	{
 		if (index_value == -1)
 		{
-			if (check_valid) goto VALID_FAIL_POISON;
+			if (failed_ref) goto VALID_FAIL_POISON;
 			RETURN_SEMA_ERROR(index, "Assigning to a compile time constant requires a constant index.");
 		}
 		expr->expr_kind = EXPR_CT_SUBSCRIPT;
@@ -3982,7 +3981,7 @@ static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr
 			Decl *len = sema_find_untyped_operator(current_expr->type, OVERLOAD_LEN, NULL);
 			if (!len)
 			{
-				if (check_valid) goto VALID_FAIL_POISON;
+				if (failed_ref) goto VALID_FAIL_POISON;
 				RETURN_SEMA_ERROR(subscripted, "Cannot index '%s' from the end, since there is no 'len' overload.", type_to_error_string(subscripted->type));
 			}
 			if (!sema_analyse_expr(context, current_expr)) return false;
@@ -4016,9 +4015,9 @@ static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr
 	// Check range
 	bool remove_from_back = false;
 	if (!sema_slice_index_is_in_range(context, current_type, index, false, start_from_end, &remove_from_back,
-	                                  check_valid))
+	                                  failed_ref != NULL))
 	{
-		if (check_valid) goto VALID_FAIL_POISON;
+		if (failed_ref) goto VALID_FAIL_POISON;
 		return false;
 	}
 	if (remove_from_back)
@@ -4030,8 +4029,8 @@ static inline bool sema_expr_analyse_subscript_lvalue(SemaContext *context, Expr
 	expr->type = type_add_optional(subscript_type, optional);
 	return true;
 VALID_FAIL_POISON:
-	expr_poison(expr);
-	return true;
+	*failed_ref = true;
+	return false;
 }
 
 static inline bool sema_expr_analyse_subscript(SemaContext *context, Expr *expr, CheckType check, bool check_valid)
@@ -5963,7 +5962,7 @@ static inline bool sema_expr_analyse_swizzle(SemaContext *context, Expr *expr, E
 		};
 		if (is_lvalue)
 		{
-			if (!sema_expr_analyse_subscript_lvalue(context, expr, false)) return false;
+			if (!sema_expr_analyse_subscript_lvalue(context, expr, NULL)) return false;
 		}
 		else
 		{
@@ -9193,7 +9192,7 @@ static inline bool sema_expr_analyse_binary(SemaContext *context, Type *infer_ty
 	{
 		if (left->expr_kind != EXPR_TYPEINFO)
 		{
-			if (!sema_analyse_expr_lvalue(context, left, NULL)) return false;
+			if (!sema_analyse_expr_lvalue(context, left, failed_ref)) return false;
 		}
 	}
 	else
@@ -11454,7 +11453,7 @@ RETRY:
 		case EXPR_CT_IDENT:
 			return sema_expr_resolve_ct_identifier(context, expr);
 		case EXPR_SUBSCRIPT:
-			return sema_expr_analyse_subscript_lvalue(context, expr, false);
+			return sema_expr_analyse_subscript_lvalue(context, expr, failed_ref);
 		case EXPR_OTHER_CONTEXT:
 		{
 			DEBUG_LOG("Switch context");
diff --git a/test/test_suite/compile_time_introspection/defined_subscript_assign.c3 b/test/test_suite/compile_time_introspection/defined_subscript_assign.c3
new file mode 100644
index 000000000..ee696e61a
--- /dev/null
+++ b/test/test_suite/compile_time_introspection/defined_subscript_assign.c3
@@ -0,0 +1,14 @@
+fn int main(String[] args)
+{
+	MyArray a = {{1, 4, 3, 6, 5}};
+	$assert(!$defined(a[0] = 2));
+	return 0;
+}
+
+struct MyArray
+{
+	int[] val;
+}
+
+fn int MyArray.get(self, usz idx) @operator([]) => self.val[idx];
+fn usz MyArray.len(self) @operator(len) => self.val.len;
\ No newline at end of file