diff --git a/lib/cargo/error.hpp b/lib/cargo/error.hpp
index fe9ee8689706948ca2fb0d6f323ad6cc18cd8724..598944be551b4a31a95465774b9c0d55b914fdbb 100644
--- a/lib/cargo/error.hpp
+++ b/lib/cargo/error.hpp
@@ -44,6 +44,8 @@ class error_code {
         not_implemented = 2,
         no_such_transfer = 3,
         transfer_in_progress = 4,
+        /* ... */
+        other = 127,
     };
 
 public:
@@ -52,6 +54,8 @@ public:
     static const error_code not_implemented;
     static const error_code no_such_transfer;
     static const error_code transfer_in_progress;
+    /* ... */
+    static const error_code other;
 
     constexpr error_code() : error_code(error_value::success) {}
     constexpr explicit error_code(error_value v)
@@ -99,6 +103,8 @@ constexpr error_code error_code::no_such_transfer{
         error_value::no_such_transfer};
 constexpr error_code error_code::transfer_in_progress{
         error_value::transfer_in_progress};
+/* ... */
+constexpr error_code error_code::other{error_value::other};
 
 static constexpr cargo::error_code
 make_system_error(std::uint32_t ec) {
diff --git a/lib/error.cpp b/lib/error.cpp
index 9987a4572d91fade361b61a74902c22beb74d56f..851b5754a59ac9879ef01f55d088bd65d71ac046 100644
--- a/lib/error.cpp
+++ b/lib/error.cpp
@@ -281,6 +281,9 @@ error_code::name() const {
             return "CARGO_NO_SUCH_TRANSFER";
         case error_value::transfer_in_progress:
             return "CARGO_TRANSFER_IN_PROGRESS";
+            /* ... */
+        case error_value::other:
+            return "CARGO_OTHER";
         default:
             return "CARGO_UNKNOWN_ERROR";
     }
@@ -302,6 +305,9 @@ error_code::message() const {
                     return "no such transfer";
                 case error_value::transfer_in_progress:
                     return "transfer in progress";
+                    /* ... */
+                case error_value::other:
+                    return "other";
                 default:
                     return "unknown error";
             }
diff --git a/src/worker/mpio_read.cpp b/src/worker/mpio_read.cpp
index dedd28428a80e19e55ec8c116a4430704d0121b1..1c6bbd0e4b187bd13069bd8c677f99dbfb41de44 100644
--- a/src/worker/mpio_read.cpp
+++ b/src/worker/mpio_read.cpp
@@ -144,8 +144,12 @@ mpio_read::operator()() const {
     } catch(const posix_file::io_error& e) {
         LOGGER_ERROR("{}() failed: {}", e.where(), e.what());
         return make_system_error(e.error_code());
+    } catch (const std::system_error& e) {
+        LOGGER_ERROR("Unexpected system error: {}", e.what());
+        return make_system_error(e.code().value());
     } catch(const std::exception& e) {
-        std::cerr << e.what() << '\n';
+        LOGGER_ERROR("Unexpected exception: {}", e.what());
+        return error_code::other;
     }
 
     return error_code::success;
diff --git a/src/worker/mpio_write.cpp b/src/worker/mpio_write.cpp
index 26cb8125bad24ae9abc8306ea3d0b6843d72c1ab..5f40048faaecf7c60d3a632446c0f19bb6e04e2e 100644
--- a/src/worker/mpio_write.cpp
+++ b/src/worker/mpio_write.cpp
@@ -146,8 +146,12 @@ mpio_write::operator()() const {
     } catch(const posix_file::io_error& e) {
         LOGGER_ERROR("{}() failed: {}", e.where(), e.what());
         return make_system_error(e.error_code());
+    } catch (const std::system_error& e) {
+        LOGGER_ERROR("Unexpected system error: {}", e.what());
+        return make_system_error(e.code().value());
     } catch(const std::exception& e) {
-        std::cerr << e.what() << '\n';
+        LOGGER_ERROR("Unexpected exception: {}", e.what());
+        return error_code::other;
     }
 
     return error_code::success;
diff --git a/tests/tests.cpp b/tests/tests.cpp
index 6ec9d742c7b90f22b420b7b8f840c24559481883..e2b235784eb32c4301ab4aa590b62e57709069b5 100644
--- a/tests/tests.cpp
+++ b/tests/tests.cpp
@@ -40,11 +40,15 @@
 using namespace std::literals;
 using namespace std::chrono_literals;
 
-std::ostream&
-operator<<(std::ostream& os, const cargo::error_code& ec) {
-    os << ec.name();
-    return os;
-}
+namespace Catch {
+template <>
+struct StringMaker<cargo::error_code> {
+    static std::string
+    convert(const cargo::error_code& ec) {
+        return std::string{ec.name()};
+    }
+};
+} // namespace Catch
 
 CATCH_REGISTER_ENUM(cargo::transfer_state, cargo::transfer_state::pending,
                     cargo::transfer_state::running,
@@ -240,6 +244,7 @@ SCENARIO("Parallel reads", "[flex_stager][parallel_reads]") {
             // wait for the transfer to complete
             auto s = tx.wait();
 
+            CAPTURE(s.error());
             REQUIRE(s.state() == cargo::transfer_state::completed);
             REQUIRE(s.error() == cargo::error_code::success);
 
@@ -301,6 +306,7 @@ SCENARIO("Parallel writes", "[flex_stager][parallel_writes]") {
             // wait for the transfer to complete
             auto s = tx.wait();
 
+            CAPTURE(s.error());
             REQUIRE(s.state() == cargo::transfer_state::completed);
             REQUIRE(s.error() == cargo::error_code::success);