diff --git a/CHANGELOG.md b/CHANGELOG.md
index 458adaa..418296c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changes
 
+* 2.0.next in progress
+  * Tentative fix for #315 by expanding `:in` handling to deal with `nil` values.
+
 * 2.0.0-beta1 (for testing; 2021-04-09)
   * Since Alpha 3, more documentation has been written and existing documentation clarified (addressing #300, #309, #313, #314).
   * Fix #319 by ensuring `register-clause!` is idempotent.
diff --git a/src/honey/sql.cljc b/src/honey/sql.cljc
index 6d99710..12b951e 100644
--- a/src/honey/sql.cljc
+++ b/src/honey/sql.cljc
@@ -921,17 +921,34 @@
     x))
 
 (defn- format-in [in [x y]]
-  (let [[sql-x & params-x] (format-expr x {:nested true})
-        [sql-y & params-y] (format-expr y {:nested true})
+  (let [nil-check          (and (sequential? y) (not (ident? (first y))))
+        y'                 (if nil-check (remove nil? y) y)
+        [sql-x & params-x] (format-expr x {:nested true})
+        [sql-y & params-y] (format-expr y' {:nested true})
         values             (unwrap (first params-y) {})]
     (if (and (= "?" sql-y) (= 1 (count params-y)) (coll? values))
-      (let [sql (str "(" (str/join ", " (repeat (count values) "?")) ")")]
-        (-> [(str sql-x " " (sql-kw in) " " sql)]
+      (let [values' (remove nil? values)
+            sql     (str "(" (str/join ", " (repeat (count values') "?")) ")")
+            in      (str sql-x " " (sql-kw in) " " sql)]
+        (-> [(if (not= (count values) (count values'))
+               (if (zero? (count values'))
+                 (str sql-x " IS NULL")
+                 (str "(" in " OR " sql-x " IS NULL)"))
+               (if (zero? (count values))
+                 "FALSE"
+                 in))]
             (into params-x)
-            (into values)))
-      (-> [(str sql-x " " (sql-kw in) " " sql-y)]
-          (into params-x)
-          (into params-y)))))
+            (into values')))
+      (let [in (str sql-x " " (sql-kw in) " " sql-y)]
+        (-> [(if (and nil-check (not= (count y) (count y')))
+               (if (zero? (count y'))
+                 (str sql-x " IS NULL")
+                 (str "(" in " OR " sql-x " IS NULL)"))
+               (if (zero? (count y))
+                 "FALSE"
+                 in))]
+            (into params-x)
+            (into params-y))))))
 
 (defn- function-0 [k xs]
   [(str (sql-kw k)
diff --git a/test/honey/sql/helpers_test.cljc b/test/honey/sql/helpers_test.cljc
index 8daa0eb..b69599f 100644
--- a/test/honey/sql/helpers_test.cljc
+++ b/test/honey/sql/helpers_test.cljc
@@ -274,6 +274,39 @@
                               :from [:customers]
                               :where [:in :id values]})))
           (is (= ["SELECT * FROM customers WHERE id IN (?)" 1]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id :?ids]}
+                             {:params {:ids values}})))))
+      (testing (str "with just a nil value from a " (name cname))
+        (let [values (conj coll nil)]
+          (is (= ["SELECT * FROM customers WHERE id IS NULL"]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id values]})))
+          (is (= ["SELECT * FROM customers WHERE id IS NULL"]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id :?ids]}
+                             {:params {:ids values}})))))
+      (testing (str "with nil values from a " (name cname))
+        (let [values (conj coll 1 nil)]
+          (is (= ["SELECT * FROM customers WHERE (id IN (?) OR id IS NULL)" 1]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id values]})))
+          (is (= ["SELECT * FROM customers WHERE (id IN (?) OR id IS NULL)" 1]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id :?ids]}
+                             {:params {:ids values}})))))
+      (testing (str "with no values from a " (name cname))
+        (let [values coll]
+          (is (= ["SELECT * FROM customers WHERE FALSE"]
+                 (sql/format {:select [:*]
+                              :from [:customers]
+                              :where [:in :id values]})))
+          (is (= ["SELECT * FROM customers WHERE FALSE"]
                  (sql/format {:select [:*]
                               :from [:customers]
                               :where [:in :id :?ids]}
@@ -285,6 +318,16 @@
                             :from [:customers]
                             :where [:in :id values]})))
         (is (= ["SELECT * FROM customers WHERE id IN (?, ?)" 1 2]
+               (sql/format {:select [:*]
+                            :from [:customers]
+                            :where [:in :id :?ids]}
+                           {:params {:ids values}}))))
+      (let [values [1 nil 2]]
+        (is (= ["SELECT * FROM customers WHERE (id IN (?, ?) OR id IS NULL)" 1 2]
+               (sql/format {:select [:*]
+                            :from [:customers]
+                            :where [:in :id values]})))
+        (is (= ["SELECT * FROM customers WHERE (id IN (?, ?) OR id IS NULL)" 1 2]
                (sql/format {:select [:*]
                             :from [:customers]
                             :where [:in :id :?ids]}