diff --git a/config.go b/config.go
index 8a84bc9..6876ba5 100644
--- a/config.go
+++ b/config.go
@@ -284,7 +284,10 @@ func walCallback(ctx context.Context, mod api.Module, _, pDB, zSchema uint32, pa
 //
 // https://sqlite.org/c3ref/autovacuum_pages.html
 func (c *Conn) AutoVacuumPages(cb func(schema string, dbPages, freePages, bytesPerPage uint) uint) error {
-	funcPtr := util.AddHandle(c.ctx, cb)
+	var funcPtr uint32
+	if cb != nil {
+		funcPtr = util.AddHandle(c.ctx, cb)
+	}
 	r := c.call("sqlite3_autovacuum_pages_go", uint64(c.handle), uint64(funcPtr))
 	return c.error(r)
 }
diff --git a/embed/bcw2/bcw2.wasm b/embed/bcw2/bcw2.wasm
index 5805df4..eeaab47 100755
Binary files a/embed/bcw2/bcw2.wasm and b/embed/bcw2/bcw2.wasm differ
diff --git a/embed/sqlite3.wasm b/embed/sqlite3.wasm
index 47aa1ae..6b388a3 100755
Binary files a/embed/sqlite3.wasm and b/embed/sqlite3.wasm differ
diff --git a/func.go b/func.go
index 4eac249..7ff740d 100644
--- a/func.go
+++ b/func.go
@@ -44,9 +44,12 @@ func (c Conn) AnyCollationNeeded() error {
 //
 // https://sqlite.org/c3ref/create_collation.html
 func (c *Conn) CreateCollation(name string, fn func(a, b []byte) int) error {
+	var funcPtr uint32
 	defer c.arena.mark()()
 	namePtr := c.arena.string(name)
-	funcPtr := util.AddHandle(c.ctx, fn)
+	if fn != nil {
+		funcPtr = util.AddHandle(c.ctx, fn)
+	}
 	r := c.call("sqlite3_create_collation_go",
 		uint64(c.handle), uint64(namePtr), uint64(funcPtr))
 	return c.error(r)
@@ -56,9 +59,12 @@ func (c *Conn) CreateCollation(name string, fn func(a, b []byte) int) error {
 //
 // https://sqlite.org/c3ref/create_function.html
 func (c *Conn) CreateFunction(name string, nArg int, flag FunctionFlag, fn ScalarFunction) error {
+	var funcPtr uint32
 	defer c.arena.mark()()
 	namePtr := c.arena.string(name)
-	funcPtr := util.AddHandle(c.ctx, fn)
+	if fn != nil {
+		funcPtr = util.AddHandle(c.ctx, fn)
+	}
 	r := c.call("sqlite3_create_function_go",
 		uint64(c.handle), uint64(namePtr), uint64(nArg),
 		uint64(flag), uint64(funcPtr))
@@ -75,10 +81,13 @@ type ScalarFunction func(ctx Context, arg ...Value)
 //
 // https://sqlite.org/c3ref/create_function.html
 func (c *Conn) CreateWindowFunction(name string, nArg int, flag FunctionFlag, fn func() AggregateFunction) error {
+	var funcPtr uint32
 	defer c.arena.mark()()
-	call := "sqlite3_create_aggregate_function_go"
 	namePtr := c.arena.string(name)
-	funcPtr := util.AddHandle(c.ctx, fn)
+	if fn != nil {
+		funcPtr = util.AddHandle(c.ctx, fn)
+	}
+	call := "sqlite3_create_aggregate_function_go"
 	if _, ok := fn().(WindowFunction); ok {
 		call = "sqlite3_create_window_function_go"
 	}
@@ -188,11 +197,12 @@ func callbackAggregate(db *Conn, pAgg, pApp uint32) (AggregateFunction, uint32)
 
 	// We need to create the aggregate.
 	fn := util.GetHandle(db.ctx, pApp).(func() AggregateFunction)()
-	handle := util.AddHandle(db.ctx, fn)
 	if pAgg != 0 {
+		handle := util.AddHandle(db.ctx, fn)
 		util.WriteUint32(db.mod, pAgg, handle)
+		return fn, handle
 	}
-	return fn, handle
+	return fn, 0
 }
 
 func callbackArgs(db *Conn, arg []Value, pArg uint32) {
diff --git a/internal/util/handle.go b/internal/util/handle.go
index 4584324..e4e3385 100644
--- a/internal/util/handle.go
+++ b/internal/util/handle.go
@@ -35,17 +35,22 @@ func DelHandle(ctx context.Context, id uint32) error {
 	s := ctx.Value(moduleKey{}).(*moduleState)
 	a := s.handles[^id]
 	s.handles[^id] = nil
-	s.holes++
+	if l := uint32(len(s.handles)); l == ^id {
+		s.handles = s.handles[:l-1]
+	} else {
+		s.holes++
+	}
 	if c, ok := a.(io.Closer); ok {
 		return c.Close()
 	}
 	return nil
 }
 
-func AddHandle(ctx context.Context, a any) (id uint32) {
+func AddHandle(ctx context.Context, a any) uint32 {
 	if a == nil {
 		panic(NilErr)
 	}
+
 	s := ctx.Value(moduleKey{}).(*moduleState)
 
 	// Find an empty slot.
diff --git a/sqlite3/column.c b/sqlite3/column.c
index c876f07..a319d27 100644
--- a/sqlite3/column.c
+++ b/sqlite3/column.c
@@ -22,6 +22,7 @@ int sqlite3_columns_go(sqlite3_stmt *stmt, int nCol, char *aType,
     switch (aType[i] = sqlite3_column_type(stmt, i)) {
       default:  // SQLITE_NULL
         aData[i] = (union sqlite3_data){};
+        continue;
       case SQLITE_INTEGER:
         aData[i].i = sqlite3_column_int64(stmt, i);
         continue;
diff --git a/sqlite3/func.c b/sqlite3/func.c
index 240ec3e..9bb830c 100644
--- a/sqlite3/func.c
+++ b/sqlite3/func.c
@@ -53,6 +53,9 @@ int sqlite3_collation_needed_go(sqlite3 *db, bool enable) {
 }
 
 int sqlite3_create_collation_go(sqlite3 *db, const char *name, go_handle app) {
+  if (app == NULL) {
+    return sqlite3_create_collation_v2(db, name, SQLITE_UTF8, NULL, NULL, NULL);
+  }
   int rc = sqlite3_create_collation_v2(db, name, SQLITE_UTF8, app, go_compare,
                                        go_destroy);
   if (rc) go_destroy(app);
@@ -61,6 +64,10 @@ int sqlite3_create_collation_go(sqlite3 *db, const char *name, go_handle app) {
 
 int sqlite3_create_function_go(sqlite3 *db, const char *name, int argc,
                                int flags, go_handle app) {
+  if (app == NULL) {
+    return sqlite3_create_function_v2(db, name, argc, SQLITE_UTF8 | flags, NULL,
+                                      NULL, NULL, NULL, NULL);
+  }
   return sqlite3_create_function_v2(db, name, argc, SQLITE_UTF8 | flags, app,
                                     go_func_wrapper, /*step=*/NULL,
                                     /*final=*/NULL, go_destroy);
@@ -68,6 +75,10 @@ int sqlite3_create_function_go(sqlite3 *db, const char *name, int argc,
 
 int sqlite3_create_aggregate_function_go(sqlite3 *db, const char *name,
                                          int argc, int flags, go_handle app) {
+  if (app == NULL) {
+    return sqlite3_create_function_v2(db, name, argc, SQLITE_UTF8 | flags, NULL,
+                                      NULL, NULL, NULL, NULL);
+  }
   return sqlite3_create_function_v2(db, name, argc, SQLITE_UTF8 | flags, app,
                                     /*func=*/NULL, go_step_wrapper,
                                     go_final_wrapper, go_destroy);
@@ -75,6 +86,10 @@ int sqlite3_create_aggregate_function_go(sqlite3 *db, const char *name,
 
 int sqlite3_create_window_function_go(sqlite3 *db, const char *name, int argc,
                                       int flags, go_handle app) {
+  if (app == NULL) {
+    return sqlite3_create_window_function(db, name, argc, SQLITE_UTF8 | flags,
+                                          NULL, NULL, NULL, NULL, NULL, NULL);
+  }
   return sqlite3_create_window_function(
       db, name, argc, SQLITE_UTF8 | flags, app, go_step_wrapper,
       go_final_wrapper, go_value_wrapper, go_inverse_wrapper, go_destroy);
diff --git a/sqlite3/hooks.c b/sqlite3/hooks.c
index 4acc2fd..1bdb405 100644
--- a/sqlite3/hooks.c
+++ b/sqlite3/hooks.c
@@ -57,9 +57,10 @@ int sqlite3_config_log_go(bool enable) {
 }
 
 int sqlite3_autovacuum_pages_go(sqlite3 *db, go_handle app) {
-  int rc = sqlite3_autovacuum_pages(db, go_autovacuum_pages, app, go_destroy);
-  if (rc) go_destroy(app);
-  return rc;
+  if (app == NULL) {
+    return sqlite3_autovacuum_pages(db, NULL, NULL, NULL);
+  }
+  return sqlite3_autovacuum_pages(db, go_autovacuum_pages, app, go_destroy);
 }
 
 #ifndef sqliteBusyCallback
diff --git a/sqlite3/vtab.c b/sqlite3/vtab.c
index 9f7421a..29735f2 100644
--- a/sqlite3/vtab.c
+++ b/sqlite3/vtab.c
@@ -163,6 +163,10 @@ static int go_vtab_shadown_name_wrapper(const char *zName) { return true; }
 
 int sqlite3_create_module_go(sqlite3 *db, const char *zName, int flags,
                              go_handle handle) {
+  if (handle == NULL) {
+    return sqlite3_create_module_v2(db, zName, NULL, NULL, NULL);
+  }
+
   struct go_module *mod = malloc(sizeof(struct go_module));
   if (mod == NULL) {
     go_destroy(handle);
diff --git a/tests/func_test.go b/tests/func_test.go
index acedc86..0a74d9e 100644
--- a/tests/func_test.go
+++ b/tests/func_test.go
@@ -209,6 +209,24 @@ func TestCreateFunction_error(t *testing.T) {
 	stmt.Step()
 }
 
+func TestCreateFunction_delete(t *testing.T) {
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.CreateFunction("regexp", 2, 0, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`SELECT 'a' REGEXP 'a|b'`)
+	if err == nil {
+		t.Error("want error")
+	}
+}
+
 func TestOverloadFunction(t *testing.T) {
 	t.Parallel()
 
diff --git a/tests/vtab_test.go b/tests/vtab_test.go
new file mode 100644
index 0000000..9266f73
--- /dev/null
+++ b/tests/vtab_test.go
@@ -0,0 +1,20 @@
+package tests
+
+import (
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+func TestCreateModule_delete(t *testing.T) {
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = sqlite3.CreateModule[sqlite3.VTab](db, "generate_series", nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/vtab.go b/vtab.go
index 80b3a33..2bb294b 100644
--- a/vtab.go
+++ b/vtab.go
@@ -57,9 +57,12 @@ func CreateModule[T VTab](db *Conn, name string, create, connect VTabConstructor
 		flags |= VTAB_SHADOWTABS
 	}
 
+	var modulePtr uint32
 	defer db.arena.mark()()
 	namePtr := db.arena.string(name)
-	modulePtr := util.AddHandle(db.ctx, module[T]{create, connect})
+	if connect != nil {
+		modulePtr = util.AddHandle(db.ctx, module[T]{create, connect})
+	}
 	r := db.call("sqlite3_create_module_go", uint64(db.handle),
 		uint64(namePtr), uint64(flags), uint64(modulePtr))
 	return db.error(r)