diff --git a/preserves.nimble b/preserves.nimble
index 054a17e..cb5e18d 100644
--- a/preserves.nimble
+++ b/preserves.nimble
@@ -1,6 +1,6 @@
 # Package
 
-version = "20230530"
+version = "20230607"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"
diff --git a/src/preserves/preserves_schema_nim.nim b/src/preserves/preserves_schema_nim.nim
index 6b83dae..b683c14 100644
--- a/src/preserves/preserves_schema_nim.nim
+++ b/src/preserves/preserves_schema_nim.nim
@@ -717,6 +717,8 @@ proc collectRefImports(imports: var StringSet; loc: Location; pat: Pattern)
 
 proc collectRefImports(imports: var StringSet; loc: Location; sp: SimplePattern) =
   case sp.orKind
+  of SimplePatternKind.setof:
+    incl(imports, "std/sets")
   of SimplePatternKind.dictof:
     incl(imports, "std/tables")
   of SimplePatternKind.Ref: