diff --git a/message_ix_models/report/__init__.py b/message_ix_models/report/__init__.py
index 1af57e7d9d..0e5ddb264d 100644
--- a/message_ix_models/report/__init__.py
+++ b/message_ix_models/report/__init__.py
@@ -369,6 +369,9 @@ def prepare_reporter(
     )
     rep.configure(model=deepcopy(context.model))
 
+    # Add a placeholder task to concatenate IAMC-structured data
+    rep.add("all::iamc", "concat")
+
     # Apply callbacks for other modules which define additional reporting computations
     for callback in chain(CALLBACKS, context.report.iter_callbacks()):
         callback(rep, context)
diff --git a/message_ix_models/report/compat.py b/message_ix_models/report/compat.py
index 9e0d198b1b..8690a5e030 100644
--- a/message_ix_models/report/compat.py
+++ b/message_ix_models/report/compat.py
@@ -416,6 +416,10 @@ def full(name: str) -> Key:
     info = dict(variable="transport emissions", base=k1.drop("h", "m", "yv"), var=[var])
     iamc(rep, info)
 
+    # Append to the "all::iamc" task
+    # TODO Use a helper function for this
+    rep.graph["all::iamc"] += ("transport emissions::iamc",)
+
     # TODO use store_ts() to store on scenario
 
     log.info(f"Added {len(rep.graph) - N} keys")