diff --git a/src/bus/driver.c b/src/bus/driver.c
index 1fd08805..373172e2 100644
--- a/src/bus/driver.c
+++ b/src/bus/driver.c
@@ -329,7 +329,7 @@ static int driver_monitor(Bus *bus, Peer *sender, Message *message) {
         filter.member = message->metadata.fields.member,
         filter.path = message->metadata.fields.path;
 
-        for (size_t i = 0; i < 64; ++i) {
+        for (size_t i = 0; i < message->metadata.n_args; ++i) {
                 if (message->metadata.args[i].element == 's') {
                         filter.args[i] = message->metadata.args[i].value;
                         filter.argpaths[i] = message->metadata.args[i].value;
diff --git a/src/bus/peer.c b/src/bus/peer.c
index cdd7aaa7..d9161660 100644
--- a/src/bus/peer.c
+++ b/src/bus/peer.c
@@ -773,7 +773,7 @@ int peer_broadcast(PolicySnapshot *sender_policy, NameSet *sender_names, MatchRe
                 filter->member = message->metadata.fields.member,
                 filter->path = message->metadata.fields.path;
 
-                for (size_t i = 0; i < 64; ++i) {
+                for (size_t i = 0; i < message->metadata.n_args; ++i) {
                         if (message->metadata.args[i].element == 's') {
                                 filter->args[i] = message->metadata.args[i].value;
                                 filter->argpaths[i] = message->metadata.args[i].value;
diff --git a/src/dbus/message.c b/src/dbus/message.c
index 59b81078..3fd23a64 100644
--- a/src/dbus/message.c
+++ b/src/dbus/message.c
@@ -385,6 +385,7 @@ static int message_parse_body(Message *message, MessageMetadata *metadata) {
                         if (i < C_ARRAY_SIZE(metadata->args)) {
                                 metadata->args[i].element = t->element;
                                 c_dvar_read(&v, (char[2]){ t->element, 0 }, &metadata->args[i].value);
+                                metadata->n_args = i + 1;
                                 break;
                         }
 
diff --git a/src/dbus/message.h b/src/dbus/message.h
index cc6cd60e..4125334b 100644
--- a/src/dbus/message.h
+++ b/src/dbus/message.h
@@ -56,6 +56,7 @@ struct MessageMetadata {
                 char element;
                 const void *value;
         } args[64];
+        size_t n_args;
 };
 
 struct Message {