diff --git a/spec/ROOT b/spec/ROOT
index afd66df05..f05baca97 100644
--- a/spec/ROOT
+++ b/spec/ROOT
@@ -110,6 +110,7 @@ session DSpec in capDL = Word_Lib +
   sessions
     ExecSpec
     ASpec
+    "HOL-Combinatorics" (* for Fun.swap *)
   theories
     Syscall_D
 
diff --git a/spec/capDL/Types_D.thy b/spec/capDL/Types_D.thy
index 91c5ec612..86d03959e 100644
--- a/spec/capDL/Types_D.thy
+++ b/spec/capDL/Types_D.thy
@@ -16,6 +16,7 @@ imports
   "ASpec.VMRights_A"
   Intents_D
   "Lib.SplitRule"
+  "HOL-Combinatorics.Transposition" (* for Fun.swap *)
 begin
 
 (* A hardware IRQ number. *)