diff --git a/internal/cutil/cutil.go b/internal/cutil/cutil.go
deleted file mode 100644
index ae55f86..0000000
--- a/internal/cutil/cutil.go
+++ /dev/null
@@ -1,14 +0,0 @@
-package cutil
-
-import "unsafe"
-
-// VoidPtr casts a uintptr value to an unsafe.Pointer value in order to use it
-// directly as a void* argument in a C function call.
-// CAUTION: NEVER store the result in a variable, or the Go GC could panic.
-func VoidPtr(i uintptr) unsafe.Pointer {
-	var nullPtr unsafe.Pointer
-	// It's not possible to cast uintptr directly to unsafe.Pointer. Therefore we
-	// cast a null pointer to uintptr and apply pointer arithmetic on it, which
-	// allows us to cast it back to unsafe.Pointer.
-	return unsafe.Pointer(uintptr(nullPtr) + i)
-}
diff --git a/internal/cutil/cutil_test.go b/internal/cutil/cutil_test.go
deleted file mode 100644
index f996c63..0000000
--- a/internal/cutil/cutil_test.go
+++ /dev/null
@@ -1,13 +0,0 @@
-package cutil
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestVoidPtr(t *testing.T) {
-	i := uintptr(42)
-	j := uintptr(VoidPtr(i))
-	assert.Equal(t, i, j)
-}
diff --git a/rbd/diff_iterate.go b/rbd/diff_iterate.go
index 41ab9ef..19a60bc 100644
--- a/rbd/diff_iterate.go
+++ b/rbd/diff_iterate.go
@@ -7,8 +7,15 @@ package rbd
 #include <stdlib.h>
 #include <rbd/librbd.h>
 
-typedef int (*diff_iterate_callback_t)(uint64_t, size_t, int, void *);
-extern int diffIterateCallback(uint64_t, size_t, int, void *);
+extern int diffIterateCallback(uint64_t, size_t, int, uintptr_t);
+
+// inline wrapper to cast uintptr_t to void*
+static inline int wrap_rbd_diff_iterate2(rbd_image_t image,
+	const char *fromsnapname, uint64_t ofs, uint64_t len, uint8_t include_parent,
+	uint8_t whole_object, uintptr_t arg) {
+		return rbd_diff_iterate2(image, fromsnapname, ofs, len, include_parent,
+			whole_object, (void*)diffIterateCallback, (void*)arg);
+};
 */
 import "C"
 
@@ -16,7 +23,6 @@ import (
 	"unsafe"
 
 	"github.com/ceph/go-ceph/internal/callbacks"
-	"github.com/ceph/go-ceph/internal/cutil"
 )
 
 var diffIterateCallbacks = callbacks.New()
@@ -101,24 +107,23 @@ func (image *Image) DiffIterate(config DiffIterateConfig) error {
 	cbIndex := diffIterateCallbacks.Add(config)
 	defer diffIterateCallbacks.Remove(cbIndex)
 
-	ret := C.rbd_diff_iterate2(
+	ret := C.wrap_rbd_diff_iterate2(
 		image.image,
 		cSnapName,
 		C.uint64_t(config.Offset),
 		C.uint64_t(config.Length),
 		C.uint8_t(config.IncludeParent),
 		C.uint8_t(config.WholeObject),
-		C.diff_iterate_callback_t(C.diffIterateCallback),
-		cutil.VoidPtr(cbIndex))
+		C.uintptr_t(cbIndex))
 
 	return getError(ret)
 }
 
 //export diffIterateCallback
 func diffIterateCallback(
-	offset C.uint64_t, length C.size_t, exists C.int, index unsafe.Pointer) C.int {
+	offset C.uint64_t, length C.size_t, exists C.int, index uintptr) C.int {
 
-	v := diffIterateCallbacks.Lookup(uintptr(index))
+	v := diffIterateCallbacks.Lookup(index)
 	config := v.(DiffIterateConfig)
 	return C.int(config.Callback(
 		uint64(offset), uint64(length), int(exists), config.Data))
diff --git a/rbd/watchers_mimic.go b/rbd/watchers_mimic.go
index 96c31af..1204fb9 100644
--- a/rbd/watchers_mimic.go
+++ b/rbd/watchers_mimic.go
@@ -8,15 +8,19 @@ package rbd
 #cgo LDFLAGS: -lrbd
 #include <rbd/librbd.h>
 
-extern void imageWatchCallback(void *);
+extern void imageWatchCallback(uintptr_t);
+
+// inline wrapper to cast uintptr_t to void*
+static inline int wrap_rbd_update_watch(rbd_image_t image, uint64_t *handle,
+	uintptr_t arg) {
+		return rbd_update_watch(image, handle, (void*)imageWatchCallback, (void*)arg);
+	};
+
 */
 import "C"
 
 import (
-	"unsafe"
-
 	"github.com/ceph/go-ceph/internal/callbacks"
-	"github.com/ceph/go-ceph/internal/cutil"
 	"github.com/ceph/go-ceph/internal/retry"
 )
 
@@ -107,11 +111,10 @@ func (image *Image) UpdateWatch(cb WatchCallback, data interface{}) (*Watch, err
 		cbIndex: watchCallbacks.Add(wcc),
 	}
 
-	ret := C.rbd_update_watch(
+	ret := C.wrap_rbd_update_watch(
 		image.image,
 		&w.handle,
-		C.rbd_update_callback_t(C.imageWatchCallback),
-		cutil.VoidPtr(w.cbIndex))
+		C.uintptr_t(w.cbIndex))
 	if ret != 0 {
 		return nil, getError(ret)
 	}
@@ -135,8 +138,8 @@ func (w *Watch) Unwatch() error {
 }
 
 //export imageWatchCallback
-func imageWatchCallback(index unsafe.Pointer) {
-	v := watchCallbacks.Lookup(uintptr(index))
+func imageWatchCallback(index uintptr) {
+	v := watchCallbacks.Lookup(index)
 	wcc := v.(watchCallbackCtx)
 	wcc.callback(wcc.data)
 }