diff --git a/cycler/__init__.py b/cycler/__init__.py
index 94b5f71..1f05670 100644
--- a/cycler/__init__.py
+++ b/cycler/__init__.py
@@ -81,8 +81,11 @@ def _process_keys(
     r_peek: dict[K, V] = next(iter(right)) if right is not None else {}
     l_key: set[K] = set(l_peek.keys())
     r_key: set[K] = set(r_peek.keys())
-    if l_key & r_key:
-        raise ValueError("Can not compose overlapping cycles")
+    if common_keys := l_key & r_key:
+        raise ValueError(
+            f"Cannot compose overlapping cycles, duplicate key(s): {common_keys}"
+        )
+
     return l_key | r_key