diff --git a/src/include/j6/types.h b/src/include/j6/types.h
index 15d762c..587775e 100644
--- a/src/include/j6/types.h
+++ b/src/include/j6/types.h
@@ -18,6 +18,7 @@ typedef uint64_t j6_signal_t;
 typedef uint64_t j6_tag_t;
 
 #define j6_tag_system_flag    0x8000000000000000
+#define j6_tag_invalid        0x0000000000000000
 
 /// If all high bits except the last 16 are set, then the tag represents
 /// an IRQ.
diff --git a/src/kernel/syscalls/endpoint.cpp b/src/kernel/syscalls/endpoint.cpp
index 733bbb5..e4c9649 100644
--- a/src/kernel/syscalls/endpoint.cpp
+++ b/src/kernel/syscalls/endpoint.cpp
@@ -35,7 +35,12 @@ endpoint_receive(j6_handle_t handle, j6_tag_t *tag, size_t *len, void *data)
 	endpoint *e = get_handle<endpoint>(handle);
 	if (!e) return j6_err_invalid_arg;
 
-	return e->receive(tag, len, data);
+	j6_tag_t out_tag = j6_tag_invalid;
+	size_t out_len = 0;
+	j6_status_t s = e->receive(&out_tag, &out_len, data);
+	*tag = out_tag;
+	*len = out_len;
+	return s;
 }
 
 j6_status_t
@@ -51,7 +56,12 @@ endpoint_sendrecv(j6_handle_t handle, j6_tag_t *tag, size_t *len, void *data)
 	if (status != j6_status_ok)
 		return status;
 
-	return e->receive(tag, len, data);
+	j6_tag_t out_tag = j6_tag_invalid;
+	size_t out_len = 0;
+	j6_status_t s = e->receive(&out_tag, &out_len, data);
+	*tag = out_tag;
+	*len = out_len;
+	return s;
 }
 
 } // namespace syscalls