diff --git a/x264c/x264c_param.go b/x264c/x264c_param.go
index 927e5df..fdaa300 100644
--- a/x264c/x264c_param.go
+++ b/x264c/x264c_param.go
@@ -8,6 +8,10 @@ import "C"
 
 import "unsafe"
 
+const (
+	rawParamSize = C.sizeof_x264_param_t
+)
+
 // Param type.
 type Param struct {
 	// CPU flags.
@@ -168,7 +172,6 @@ type Param struct {
 	BOpencl int32
 	// Specify count of GPU devices to skip, for CLI users.
 	IOpenclDevice int32
-	_             [4]byte
 	// Pass explicit cl_device_id as void*, for API users.
 	OpenclDeviceId unsafe.Pointer
 	// Filename (in UTF-8) of the compiled OpenCL kernel cache file.
@@ -186,7 +189,6 @@ type Param struct {
 	// Absolute cap on slices per frame; stops applying slice-max-size and slice-max-mbs if this is reached.
 	ISliceCountMax int32
 
-	_           [4]byte
 	ParamFree   *[0]byte
 	NaluProcess *[0]byte
 	Opaque      unsafe.Pointer
diff --git a/x264c/x264c_param_test.go b/x264c/x264c_param_test.go
new file mode 100644
index 0000000..94a031f
--- /dev/null
+++ b/x264c/x264c_param_test.go
@@ -0,0 +1,15 @@
+package x264c
+
+import (
+	"fmt"
+	"testing"
+	"unsafe"
+)
+
+func TestRawParamSize(t *testing.T) {
+	if rawParamSize == unsafe.Sizeof(Param{}) {
+		return
+	}
+
+	t.Fatal(fmt.Sprintf("%v != %v", rawParamSize, unsafe.Sizeof(Param{})))
+}