diff --git a/src/geom.c b/src/geom.c
index 1184614..bcb178a 100644
--- a/src/geom.c
+++ b/src/geom.c
@@ -36,12 +36,6 @@ struct WinGeom win_geom_create()
  * Default init functions *
  **************************/
 
-void sizes_init(const Sizes sizes)
-{
-	sizes->w = 0;
-	sizes->h = 0;
-}
-
 void basic_geom_init(const BasicGeom basic_geom)
 {
 	position_init(&basic_geom->position);
diff --git a/src/geom.rs b/src/geom.rs
index 96c8f1a..0f7e775 100644
--- a/src/geom.rs
+++ b/src/geom.rs
@@ -6,12 +6,24 @@ pub struct Position {
     y: c_int,
 }
 
+#[repr(C)]
+pub struct Sizes {
+    width: c_int,
+    height: c_int,
+}
+
 impl Default for Position {
     fn default() -> Self {
         Self::new(0, 0)
     }
 }
 
+impl Default for Sizes {
+    fn default() -> Self {
+        Self::new(0, 0)
+    }
+}
+
 impl Position {
     fn new(x: c_int, y: c_int) -> Self {
         Self { x, y }
@@ -25,3 +37,17 @@ impl Position {
         self.y
     }
 }
+
+impl Sizes {
+    fn new(width: c_int, height: c_int) -> Self {
+        Self { width, height }
+    }
+
+    fn width(&self) -> c_int {
+        self.width
+    }
+
+    fn height(&self) -> c_int {
+        self.height
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 9175eed..e11e7c7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -58,3 +58,8 @@ extern "C" fn constraints_snap_distance(snap_distance: c_uint) -> c_uint {
 unsafe extern "C" fn position_init(position: *mut geom::Position) {
     *position = Default::default();
 }
+
+#[no_mangle]
+unsafe extern "C" fn sizes_init(sizes: &mut geom::Sizes) {
+    *sizes = Default::default();
+}