diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index be6d1837b..299a17c2a 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -2339,7 +2339,7 @@ bool sema_analyse_ct_echo_stmt(SemaContext *context, Ast *statement);
 bool sema_analyse_statement(SemaContext *context, Ast *statement);
 
 bool sema_expr_analyse_assign_right_side(SemaContext *context, Expr *expr, Type *left_type, Expr *right,
-                                         bool is_unwrapped_var, bool is_declaration);
+                                         bool is_unwrapped_var, bool is_declaration, bool *failed_ref);
 bool sema_expr_analyse_initializer_list(SemaContext *context, Type *to, Expr *expr);
 Expr **sema_expand_vasplat_exprs(SemaContext *context, Expr **exprs);
 
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 4a178f3fb..b33afab85 100755
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -4582,7 +4582,7 @@ bool sema_analyse_var_decl(SemaContext *context, Decl *decl, bool local)
 		CallEnvKind env_kind = context->call_env.kind;
 		if (is_static) context->call_env.kind = CALL_ENV_FUNCTION_STATIC;
 		decl->in_init = true;
-		if (!sema_expr_analyse_assign_right_side(context, NULL, decl->type, init, false, true))
+		if (!sema_expr_analyse_assign_right_side(context, NULL, decl->type, init, false, true, NULL))
 		{
 			context->call_env.kind = env_kind;
 			return decl_poison(decl);
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index 09195f738..2fc4bc722 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -91,7 +91,7 @@ static bool sema_expr_analyse_enum_add_sub(SemaContext *context, Expr *expr, Exp
 static bool sema_expr_analyse_shift(SemaContext *context, Expr *expr, Expr *left, Expr *right, bool *failed_ref);
 static bool sema_expr_check_shift_rhs(SemaContext *context, Expr *expr, Type *left_type, Type *left_type_flat, Expr *right, Type *right_type_flat, bool *failed_ref);
 static bool sema_expr_analyse_and_or(SemaContext *context, Expr *expr, Expr *left, Expr *right, bool *failed_ref);
-static bool sema_expr_analyse_slice_assign(SemaContext *context, Expr *expr, Type *left_type, Expr *right);
+static bool sema_expr_analyse_slice_assign(SemaContext *context, Expr *expr, Type *left_type, Expr *right, bool *failed_ref);
 static bool sema_expr_analyse_ct_identifier_assign(SemaContext *context, Expr *expr, Expr *left, Expr *right);
 static bool sema_expr_analyse_ct_type_identifier_assign(SemaContext *context, Expr *expr, Expr *left, Expr *right);
 static bool sema_expr_analyse_assign(SemaContext *context, Expr *expr, Expr *left, Expr *right, bool *failed_ref);
@@ -5986,7 +5986,7 @@ static inline bool sema_expr_analyse_cast(SemaContext *context, Expr *expr, bool
 	return true;
 }
 
-static bool sema_expr_analyse_slice_assign(SemaContext *context, Expr *expr, Type *left_type, Expr *right)
+static bool sema_expr_analyse_slice_assign(SemaContext *context, Expr *expr, Type *left_type, Expr *right, bool *failed_ref)
 {
 	Expr *left = exprptr(expr->binary_expr.left);
 	Type *left_flat = type_flatten(left_type);
@@ -6024,10 +6024,11 @@ static bool sema_expr_analyse_slice_assign(SemaContext *context, Expr *expr, Typ
 	{
 		if (right_type->array.base->canonical == base->canonical)
 		{
+			CHECK_ON_DEFINED(failed_ref);
 			RETURN_SEMA_ERROR(right, "You cannot assign a slice, vector or array to a slicing without making an explicit [..] operation, e.g. 'foo[..] = my_array[..]', so you can try adding an explicit slicing to this expression.");
 		}
 	}
-	if (!cast_implicit(context, right, base, false)) return false;
+	if (!cast_implicit_checked(context, right, base, false, failed_ref)) return false;
 	if (IS_OPTIONAL(right))
 	{
 		RETURN_SEMA_ERROR(right, "The right hand side may not be optional when using slice assign.");
@@ -6055,6 +6056,7 @@ SLICE_COPY:;
 	}
 	if (left_len >= 0 && right_len >= 0 && left_len != right_len)
 	{
+		CHECK_ON_DEFINED(failed_ref);
 		RETURN_SEMA_ERROR(expr, "Length mismatch between slices.");
 	}
 	expr->expr_kind = EXPR_SLICE_COPY;
@@ -6065,16 +6067,16 @@ SLICE_COPY:;
 }
 
 bool sema_expr_analyse_assign_right_side(SemaContext *context, Expr *expr, Type *left_type, Expr *right,
-										 bool is_unwrapped_var, bool is_declaration)
+                                         bool is_unwrapped_var, bool is_declaration, bool *failed_ref)
 {
 	if (expr && exprptr(expr->binary_expr.left)->expr_kind == EXPR_SLICE)
 	{
-		return sema_expr_analyse_slice_assign(context, expr, left_type, right);
+		return sema_expr_analyse_slice_assign(context, expr, left_type, right, failed_ref);
 	}
 
 	// 1. Evaluate right side to required type.
 	bool to_optional = left_type && type_is_optional(left_type);
-	if (!sema_analyse_expr_rhs(context, left_type, right, is_unwrapped_var || to_optional, NULL, is_declaration)) return false;
+	if (!sema_analyse_expr_rhs(context, left_type, right, is_unwrapped_var || to_optional, failed_ref, is_declaration)) return false;
 	if (IS_OPTIONAL(right) && !to_optional)
 	{
 		if (is_unwrapped_var)
@@ -6082,6 +6084,7 @@ bool sema_expr_analyse_assign_right_side(SemaContext *context, Expr *expr, Type
 			RETURN_SEMA_ERROR(exprptr(expr->binary_expr.left), "The variable is unwrapped in this context, if you don't want to unwrap it, use () around the variable to suppress unwrapping, like 'catch err = (x)' and 'try (x)'.");
 		}
 		if (!left_type) left_type = type_no_optional(right->type);
+		CHECK_ON_DEFINED(failed_ref);
 		return sema_error_failed_cast(context, right, right->type, left_type);
 	}
 
@@ -6251,7 +6254,7 @@ static bool sema_expr_analyse_assign(SemaContext *context, Expr *expr, Expr *lef
 	bool is_unwrapped_var = expr_is_unwrapped_ident(left);
 
 	// 3. Evaluate right side to required type.
-	if (!sema_expr_analyse_assign_right_side(context, expr, left->type, right, is_unwrapped_var, false)) return false;
+	if (!sema_expr_analyse_assign_right_side(context, expr, left->type, right, is_unwrapped_var, false, failed_ref)) return false;
 
 	if (is_unwrapped_var && IS_OPTIONAL(right))
 	{
diff --git a/test/unit/regression/defined.c3 b/test/unit/regression/defined.c3
index 325e59072..1ad97242f 100644
--- a/test/unit/regression/defined.c3
+++ b/test/unit/regression/defined.c3
@@ -15,4 +15,8 @@ fn void binary()
 	assert(!$defined(*1));
 	assert(!$defined(&1));
 	assert(!$defined(1 = "ofek"));
+	String[] a;
+	assert(!$defined(a[0] = 1));
+	int x;
+	assert(!$defined(x[0]));
 }
\ No newline at end of file