diff --git a/testcases/lib/SocketActivation.pm b/testcases/lib/SocketActivation.pm
index 0f307eb3..5951fd26 100644
--- a/testcases/lib/SocketActivation.pm
+++ b/testcases/lib/SocketActivation.pm
@@ -145,7 +145,12 @@ sub activate_i3 {
         if ($args{inject_randr15}) {
             # See comment in $args{strace} branch.
             $cmd = 'test.inject_randr15 --getmonitors_reply="' .
-                   $args{inject_randr15} . '" -- ' .
+                   $args{inject_randr15} . '" ' .
+                   ($args{inject_randr15_outputinfo}
+                    ? '--getoutputinfo_reply="' .
+                      $args{inject_randr15_outputinfo} . '" '
+                    : '') .
+                   '-- ' .
                    'sh -c "export LISTEN_PID=\$\$; ' . $cmd . '"';
         }
 
diff --git a/testcases/lib/i3test.pm.in b/testcases/lib/i3test.pm.in
index 18bebb52..f9b3e939 100644
--- a/testcases/lib/i3test.pm.in
+++ b/testcases/lib/i3test.pm.in
@@ -863,6 +863,7 @@ sub launch_with_config {
         dont_create_temp_dir => $args{dont_create_temp_dir},
         validate_config => $args{validate_config},
         inject_randr15 => $args{inject_randr15},
+        inject_randr15_outputinfo => $args{inject_randr15_outputinfo},
     );
 
     # If we called i3 with -C, we wait for it to exit and then return as