diff --git a/src/tmducken/duckdb.clj b/src/tmducken/duckdb.clj
index bca6938..c091252 100644
--- a/src/tmducken/duckdb.clj
+++ b/src/tmducken/duckdb.clj
@@ -343,7 +343,7 @@ tmducken.duckdb> (get-config-options)
           ;;stack resource context is mainly for the string values.
           (resource/stack-resource-context
            (let [row-offset (* chunk chunk-size)
-                 row-count (rem n-rows chunk-size)
+                 row-count (min chunk-size (- n-rows row-offset))
                  n-valid (quot (+ row-count 63) 64)
                  string-allocs (ArrayList.)
                  reduce-groups (ArrayList.)]
@@ -666,7 +666,8 @@ tmducken.duckdb> (get-config-options)
 
 (defn- destroy-chunk
   [chunk]
-  (duckdb-ffi/duckdb_destroy_data_chunk (dt-ffi/make-ptr :pointer (.address ^Pointer chunk))))
+  (when (and chunk (not (== 0 (.address ^Pointer chunk))))
+    (duckdb-ffi/duckdb_destroy_data_chunk (dt-ffi/make-ptr :pointer (.address ^Pointer chunk)))))
 
 
 (defn- reduce-chunk
@@ -752,7 +753,9 @@ tmducken.duckdb> (get-config-options)
                  (not (== 0 (.address ^Pointer chunk)))
                  (not (reduced? acc)))
           (recur (reduce-chunk chunk realize-chunk reduce-type rfn acc))
-          (if (reduced? acc) @acc acc)))))
+          (do
+            (destroy-chunk chunk)
+            (if (reduced? acc) @acc acc))))))
   Iterable
   (iterator [this] (SupplierIter. this (.get this)))
   Seqable
diff --git a/test/tmducken/duckdb_test.clj b/test/tmducken/duckdb_test.clj
index f98da37..34d8841 100644
--- a/test/tmducken/duckdb_test.clj
+++ b/test/tmducken/duckdb_test.clj
@@ -1,6 +1,7 @@
 (ns tmducken.duckdb-test
   (:require [clojure.test :refer [deftest is]]
             [tmducken.duckdb :as duckdb]
+            [tmducken.duckdb.ffi :as duckdb-ffi]
             [tech.v3.dataset :as ds]
             [tech.v3.datatype.functional :as dfn]
             [tech.v3.datatype.datetime :as dtype-dt]
@@ -135,23 +136,33 @@
         (catch Throwable e nil)))))
 
 (deftest insert-test
-  #_(println "========================================")
-  #_(println "insert-test")
   (let [cn 4
         rn 1024
         ds-fn #(-> (into {} (for [i (range cn)] [(str "c" i)
                                                  (for [_ (range rn)] (str (random-uuid)))]))
                    (ds/->dataset {:dataset-name "t"})
                    (ds/select-columns (for [i (range cn)] (str "c" i))))]
-    #_(println "drop-table!")
     (try
       (duckdb/drop-table! @conn* "t")
       (catch Throwable e nil))
     (duckdb/create-table! @conn* (ds-fn))
-    #_(println "insert-dataset! (first)")
     (duckdb/insert-dataset! @conn* (ds-fn))
-    #_(println "insert-dataset! (second)")
     (duckdb/insert-dataset! @conn* (ds-fn))
-    #_(println "insert-dataset! (sql->dataset)")
+    (is (= (* 2 rn) (-> (duckdb/sql->dataset @conn* "from t")
+                        (ds/row-count))))))
+
+(deftest insert-chunk-size-test
+  (let [cn 4
+        rn (duckdb-ffi/duckdb_vector_size)
+        ds-fn #(-> (into {} (for [i (range cn)] [(str "c" i)
+                                                 (for [_ (range rn)] (random-uuid))]))
+                   (ds/->dataset {:dataset-name "t"})
+                   (ds/select-columns (for [i (range cn)] (str "c" i))))]
+    (try
+      (duckdb/drop-table! @conn* "t")
+      (catch Throwable e nil))
+    (duckdb/create-table! @conn* (ds-fn))
+    (duckdb/insert-dataset! @conn* (ds-fn))
+    (duckdb/insert-dataset! @conn* (ds-fn))
     (is (= (* 2 rn) (-> (duckdb/sql->dataset @conn* "from t")
                         (ds/row-count))))))