diff --git a/unison-runtime/tests/Unison/Test/Runtime/MCode/Serialization.hs b/unison-runtime/tests/Unison/Test/Runtime/MCode/Serialization.hs
index 1b95a96b40..a9b82a272a 100644
--- a/unison-runtime/tests/Unison/Test/Runtime/MCode/Serialization.hs
+++ b/unison-runtime/tests/Unison/Test/Runtime/MCode/Serialization.hs
@@ -13,6 +13,7 @@ import Hedgehog hiding (Rec, Test, test)
 import Hedgehog.Gen qualified as Gen
 import Hedgehog.Range qualified as Range
 import Unison.Prelude
+import Unison.Runtime.Foreign.Function.Type (ForeignFunc)
 import Unison.Runtime.Interface
 import Unison.Runtime.MCode (Args (..), BPrim1, BPrim2, Branch, Comb, CombIx (..), GBranch (..), GComb (..), GCombInfo (..), GInstr (..), GRef (..), GSection (..), Instr, MLit (..), Ref, Section, UPrim1, UPrim2)
 import Unison.Runtime.Machine (Combs)
@@ -33,6 +34,9 @@ test =
             ]
     EasyTest.expect success
 
+genForeignCall :: Gen ForeignFunc
+genForeignCall = Gen.enumBounded
+
 genEnumMap :: (EC.EnumKey k) => Gen k -> Gen v -> Gen (EnumMap k v)
 genEnumMap genK genV = EC.mapFromList <$> Gen.list (Range.linear 0 10) ((,) <$> genK <*> genV)
 
@@ -116,7 +120,7 @@ genInstr =
       UPrim2 <$> genUPrim2 <*> genSmallInt <*> genSmallInt,
       BPrim1 <$> genBPrim1 <*> genSmallInt,
       BPrim2 <$> genBPrim2 <*> genSmallInt <*> genSmallInt,
-      ForeignCall <$> Gen.bool <*> genSmallWord64 <*> genArgs,
+      ForeignCall <$> Gen.bool <*> genForeignCall <*> genArgs,
       SetDyn <$> genSmallWord64 <*> genSmallInt,
       Capture <$> genSmallWord64,
       Name <$> genGRef <*> genArgs,