diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index a4918654..2e2333a3 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -13,7 +13,7 @@ on:
 
 jobs:
   setup:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
@@ -48,7 +48,7 @@ jobs:
               ;;
           esac
   lint:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
       - uses: actions/checkout@v4
@@ -71,7 +71,7 @@ jobs:
     needs: setup
     strategy:
       matrix: ${{fromJson(needs.setup.outputs.matrix)}}
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
       - name: Checkout
@@ -100,7 +100,7 @@ jobs:
         env:
           CMD: ${{ matrix.cmd }}
   all-pr-checks:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     needs: [test, lint]
     steps:
diff --git a/project.clj b/project.clj
index 40dba740..0e154fdb 100644
--- a/project.clj
+++ b/project.clj
@@ -20,6 +20,11 @@
                   ["change" "version" "leiningen.release/bump-version"]
                   ["vcs" "commit"]
                   ["vcs" "push"]]
+  ;; exclude ^:integration tests by default (e.g., ocsf-test/test-all-ocsf-versions requires Docker)
+  ;; run them explicitly with: lein test :integration
+  :test-selectors {:default (complement :integration)
+                   :integration :integration
+                   :all (constantly true)}
   :resource-paths ["resources"]
   :profiles {:dev
              {:resource-paths ["test-resources"]
diff --git a/src/flanders/spec.clj b/src/flanders/spec.clj
index 87428b33..d60d66b1 100644
--- a/src/flanders/spec.clj
+++ b/src/flanders/spec.clj
@@ -108,16 +108,26 @@
       map-kw))
 
   SequenceOfType
-  (->spec' [{:keys [type]} ns f]
+  (->spec' [{:keys [type spec]} ns f]
     (let [result-kw (keyword ns "seq-of")]
       (eval `(s/def ~result-kw ~(f type (str ns "." "seq-of"))))
-      (eval `(s/coll-of ~result-kw))))
+      (let [coll-spec (eval `(s/coll-of ~result-kw))]
+        (if spec
+          (s/and-spec-impl [`(s/coll-of ~result-kw) `~spec]
+                           [coll-spec spec]
+                           nil)
+          coll-spec))))
 
   SetOfType
-  (->spec' [{:keys [type]} ns f]
+  (->spec' [{:keys [type spec]} ns f]
     (let [result-kw (keyword ns "set-of")]
       (eval `(s/def ~result-kw ~(f type (str ns "." "set-of"))))
-      (eval `(s/coll-of ~result-kw :kind set?))))
+      (let [coll-spec (eval `(s/coll-of ~result-kw :kind set?))]
+        (if spec
+          (s/and-spec-impl [`(s/coll-of ~result-kw :kind set?) `~spec]
+                           [coll-spec spec]
+                           nil)
+          coll-spec))))
 
   SignatureType
   (->spec' [{:keys [parameters rest-parameter return]} ns f]
diff --git a/test/flanders/spec_test.clj b/test/flanders/spec_test.clj
index 0ca3a6cb..da4c4120 100644
--- a/test/flanders/spec_test.clj
+++ b/test/flanders/spec_test.clj
@@ -115,6 +115,48 @@
        (fs/->spec (f/set-of (f/set-of f/any-str)) "test-set")
        #{#{"foo"}})))
 
+(defn max-len [n]
+  (fn [coll] (<= (count coll) n)))
+
+(deftest test-seq-of-with-spec
+  (testing "seq-of with custom spec predicate (max length)"
+    (is (s/valid?
+         (fs/->spec (f/seq-of f/any-str :spec #(<= (count %) 3))
+                    "test-seq-spec-1")
+         ["a" "b" "c"]))
+    (is ((complement s/valid?)
+         (fs/->spec (f/seq-of f/any-str :spec #(<= (count %) 3))
+                    "test-seq-spec-2")
+         ["a" "b" "c" "d"])))
+  (testing "seq-of with closure spec (e.g. from pred/max-len)"
+    (is (s/valid?
+         (fs/->spec (f/seq-of f/any-str :spec (max-len 2))
+                    "test-seq-spec-closure-1")
+         ["a" "b"]))
+    (is ((complement s/valid?)
+         (fs/->spec (f/seq-of f/any-str :spec (max-len 2))
+                    "test-seq-spec-closure-2")
+         ["a" "b" "c"])))
+  (testing "seq-of without spec still works"
+    (is (s/valid?
+         (fs/->spec (f/seq-of f/any-str) "test-seq-spec-3")
+         ["a" "b" "c" "d"]))))
+
+(deftest test-set-of-with-spec
+  (testing "set-of with custom spec predicate (max length)"
+    (is (s/valid?
+         (fs/->spec (f/set-of f/any-str :spec #(<= (count %) 2))
+                    "test-set-spec-1")
+         #{"a" "b"}))
+    (is ((complement s/valid?)
+         (fs/->spec (f/set-of f/any-str :spec #(<= (count %) 2))
+                    "test-set-spec-2")
+         #{"a" "b" "c"})))
+  (testing "set-of without spec still works"
+    (is (s/valid?
+         (fs/->spec (f/set-of f/any-str) "test-set-spec-3")
+         #{"a" "b" "c"}))))
+
 (deftest sig-spec-test
   (let [spec-key (fs/->spec (f/sig :parameters [(f/int)]) "foo")]
     (is (match (s/describe spec-key)