diff --git a/docs/ipc b/docs/ipc
index f0829dc2..ce38a546 100644
--- a/docs/ipc
+++ b/docs/ipc
@@ -156,7 +156,7 @@ following properties:
 
 num (integer)::
 	The logical number of the workspace. Corresponds to the command
-	to switch to this workspace.
+	to switch to this workspace. For named workspaces, this will be -1.
 name (string)::
 	The name of this workspace (by default num+1), as changed by the
 	user. Encoded in UTF-8.
diff --git a/src/ipc.c b/src/ipc.c
index 03b3d5ad..6dab654c 100644
--- a/src/ipc.c
+++ b/src/ipc.c
@@ -617,10 +617,7 @@ IPC_HANDLER(get_workspaces) {
             y(map_open);
 
             ystr("num");
-            if (ws->num == -1)
-                y(null);
-            else
-                y(integer, ws->num);
+            y(integer, ws->num);
 
             ystr("name");
             ystr(ws->name);
diff --git a/testcases/t/139-ws-numbers.t b/testcases/t/139-ws-numbers.t
index 6829a147..f76ee04b 100644
--- a/testcases/t/139-ws-numbers.t
+++ b/testcases/t/139-ws-numbers.t
@@ -24,7 +24,7 @@ sub check_order {
     my ($msg) = @_;
 
     my @ws = @{$i3->get_workspaces->recv};
-    my @nums = map { $_->{num} } grep { defined($_->{num}) } @ws;
+    my @nums = map { $_->{num} } grep { $_->{num} != -1 } @ws;
     my @sorted = sort @nums;
 
     is_deeply(\@nums, \@sorted, $msg);