diff --git a/qualtran/_infra/bloq.py b/qualtran/_infra/bloq.py
index 5fda9d70c..e9d48121f 100644
--- a/qualtran/_infra/bloq.py
+++ b/qualtran/_infra/bloq.py
@@ -52,9 +52,14 @@
 def _decompose_from_build_composite_bloq(bloq: 'Bloq') -> 'CompositeBloq':
     from qualtran import BloqBuilder
 
-    bb, initial_soqs = BloqBuilder.from_signature(bloq.signature, add_registers_allowed=False)
-    out_soqs = bloq.build_composite_bloq(bb=bb, **initial_soqs)
-    return bb.finalize(**out_soqs)
+    try:
+        bb, initial_soqs = BloqBuilder.from_signature(bloq.signature, add_registers_allowed=False)
+        out_soqs = bloq.build_composite_bloq(bb=bb, **initial_soqs)
+        return bb.finalize(**out_soqs)
+    except (DecomposeTypeError, DecomposeNotImplementedError) as ex:
+        raise ex
+    except Exception as ex:
+        raise RuntimeError(f"Unexpected error when decomposing {bloq}: {ex}") from ex
 
 
 class DecomposeNotImplementedError(NotImplementedError):
diff --git a/qualtran/cirq_interop/_cirq_to_bloq.py b/qualtran/cirq_interop/_cirq_to_bloq.py
index 447227a6b..3ffc18773 100644
--- a/qualtran/cirq_interop/_cirq_to_bloq.py
+++ b/qualtran/cirq_interop/_cirq_to_bloq.py
@@ -602,8 +602,12 @@ def decompose_from_registers(
         return cirq_optree_to_cbloq(
             decomposed_optree, signature=bloq.signature, in_quregs=in_quregs, out_quregs=out_quregs
         )
+    except (DecomposeNotImplementedError, DecomposeTypeError) as exc:
+        raise exc
     except ValueError as exc:
         if "Only gate operations are supported" in str(exc):
             raise DecomposeNotImplementedError(str(exc)) from exc
         else:
-            raise exc
+            raise RuntimeError(f"Unexpected error when decomposing {bloq}: {exc}") from exc
+    except Exception as exc:
+        raise RuntimeError(f"Unexpected error when decomposing {bloq}: {exc}") from exc