diff --git a/crates/servicepoint_binding_c/src/connection.rs b/crates/servicepoint_binding_c/src/connection.rs
index 95940f8..3f54438 100644
--- a/crates/servicepoint_binding_c/src/connection.rs
+++ b/crates/servicepoint_binding_c/src/connection.rs
@@ -1,4 +1,4 @@
-//! C functions for interacting with `SPConnection`s
+//! C functions for interacting with [SPConnection]s
 //!
 //! prefix `sp_connection_`
 
@@ -24,7 +24,7 @@ pub struct SPConnection(pub(crate) servicepoint::Connection);
 ///
 /// # Panics
 ///
-/// Bad string encoding
+/// - when `host` is null or an invalid host
 ///
 /// # Safety
 ///
@@ -36,6 +36,7 @@ pub struct SPConnection(pub(crate) servicepoint::Connection);
 pub unsafe extern "C" fn sp_connection_open(
     host: *const c_char,
 ) -> *mut SPConnection {
+    assert!(!host.is_null());
     let host = CStr::from_ptr(host).to_str().expect("Bad encoding");
     let connection = match servicepoint::Connection::open(host) {
         Err(_) => return null_mut(),
@@ -51,6 +52,11 @@ pub unsafe extern "C" fn sp_connection_open(
 ///
 /// returns: true in case of success
 ///
+/// # Panics
+///
+/// - when `connection` is NULL
+/// - when `packet` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -63,16 +69,23 @@ pub unsafe extern "C" fn sp_connection_send_packet(
     connection: *const SPConnection,
     packet: *mut SPPacket,
 ) -> bool {
+    assert!(!connection.is_null());
+    assert!(!packet.is_null());
     let packet = Box::from_raw(packet);
     (*connection).0.send((*packet).0).is_ok()
 }
 
-/// Sends a [SPCommand] to the display using the `SPConnection`.
+/// Sends a [SPCommand] to the display using the [SPConnection].
 ///
 /// The passed `command` gets consumed.
 ///
 /// returns: true in case of success
 ///
+/// # Panics
+///
+/// - when `connection` is NULL
+/// - when `command` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -85,6 +98,8 @@ pub unsafe extern "C" fn sp_connection_send_command(
     connection: *const SPConnection,
     command: *mut SPCommand,
 ) -> bool {
+    assert!(!connection.is_null());
+    assert!(!command.is_null());
     let command = (*Box::from_raw(command)).0;
     (*connection).0.send(command).is_ok()
 }
@@ -93,8 +108,6 @@ pub unsafe extern "C" fn sp_connection_send_command(
 ///
 /// # Panics
 ///
-/// # Panics
-///
 /// - when `connection` is NULL
 ///
 /// # Safety
@@ -105,5 +118,6 @@ pub unsafe extern "C" fn sp_connection_send_command(
 /// - `connection` is not used concurrently or after this call
 #[no_mangle]
 pub unsafe extern "C" fn sp_connection_free(connection: *mut SPConnection) {
+    assert!(!connection.is_null());
     _ = Box::from_raw(connection);
 }
diff --git a/crates/servicepoint_binding_c/src/cp437_grid.rs b/crates/servicepoint_binding_c/src/cp437_grid.rs
index 98b1927..791c594 100644
--- a/crates/servicepoint_binding_c/src/cp437_grid.rs
+++ b/crates/servicepoint_binding_c/src/cp437_grid.rs
@@ -27,7 +27,7 @@ impl Clone for SPCp437Grid {
 
 /// Creates a new [SPCp437Grid] with the specified dimensions.
 ///
-/// returns: [SPCp437Grid] initialized to 0.
+/// returns: [SPCp437Grid] initialized to 0. Will never return NULL.
 ///
 /// # Safety
 ///
@@ -40,9 +40,11 @@ pub unsafe extern "C" fn sp_cp437_grid_new(
     width: usize,
     height: usize,
 ) -> *mut SPCp437Grid {
-    Box::into_raw(Box::new(SPCp437Grid(servicepoint::Cp437Grid::new(
+    let result = Box::into_raw(Box::new(SPCp437Grid(servicepoint::Cp437Grid::new(
         width, height,
-    ))))
+    ))));
+    assert!(!result.is_null());
+    result
 }
 
 /// Loads a [SPCp437Grid] with the specified dimensions from the provided data.
@@ -51,7 +53,8 @@ pub unsafe extern "C" fn sp_cp437_grid_new(
 ///
 /// # Panics
 ///
-/// When the provided `data_length` is not sufficient for the `height` and `width`
+/// - when `data` is NULL
+/// - when the provided `data_length` does not match `height` and `width`
 ///
 /// # Safety
 ///
@@ -68,16 +71,23 @@ pub unsafe extern "C" fn sp_cp437_grid_load(
     data: *const u8,
     data_length: usize,
 ) -> *mut SPCp437Grid {
+    assert!(data.is_null());
     let data = std::slice::from_raw_parts(data, data_length);
-    Box::into_raw(Box::new(SPCp437Grid(servicepoint::Cp437Grid::load(
+    let result = Box::into_raw(Box::new(SPCp437Grid(servicepoint::Cp437Grid::load(
         width, height, data,
-    ))))
+    ))));
+    assert!(!result.is_null());
+    result
 }
 
 /// Clones a [SPCp437Grid].
 ///
 /// Will never return NULL.
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -90,11 +100,18 @@ pub unsafe extern "C" fn sp_cp437_grid_load(
 pub unsafe extern "C" fn sp_cp437_grid_clone(
     cp437_grid: *const SPCp437Grid,
 ) -> *mut SPCp437Grid {
-    Box::into_raw(Box::new((*cp437_grid).clone()))
+    assert!(!cp437_grid.is_null());
+    let result = Box::into_raw(Box::new((*cp437_grid).clone()));
+    assert!(!result.is_null());
+    result
 }
 
 /// Deallocates a [SPCp437Grid].
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -104,6 +121,7 @@ pub unsafe extern "C" fn sp_cp437_grid_clone(
 /// - `cp437_grid` was not passed to another consuming function, e.g. to create a [SPCommand]
 #[no_mangle]
 pub unsafe extern "C" fn sp_cp437_grid_free(cp437_grid: *mut SPCp437Grid) {
+    assert!(!cp437_grid.is_null());
     _ = Box::from_raw(cp437_grid);
 }
 
@@ -116,7 +134,8 @@ pub unsafe extern "C" fn sp_cp437_grid_free(cp437_grid: *mut SPCp437Grid) {
 ///
 /// # Panics
 ///
-/// When accessing `x` or `y` out of bounds.
+/// - when `cp437_grid` is NULL
+/// - when accessing `x` or `y` out of bounds
 ///
 /// # Safety
 ///
@@ -130,6 +149,7 @@ pub unsafe extern "C" fn sp_cp437_grid_get(
     x: usize,
     y: usize,
 ) -> u8 {
+    assert!(!cp437_grid.is_null());
     (*cp437_grid).0.get(x, y)
 }
 
@@ -145,7 +165,8 @@ pub unsafe extern "C" fn sp_cp437_grid_get(
 ///
 /// # Panics
 ///
-/// When accessing `x` or `y` out of bounds.
+/// - when `cp437_grid` is NULL
+/// - when accessing `x` or `y` out of bounds
 ///
 /// # Safety
 ///
@@ -160,6 +181,7 @@ pub unsafe extern "C" fn sp_cp437_grid_set(
     y: usize,
     value: u8,
 ) {
+    assert!(!cp437_grid.is_null());
     (*cp437_grid).0.set(x, y, value);
 }
 
@@ -170,6 +192,10 @@ pub unsafe extern "C" fn sp_cp437_grid_set(
 /// - `cp437_grid`: instance to write to
 /// - `value`: the value to set all cells to
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -181,6 +207,7 @@ pub unsafe extern "C" fn sp_cp437_grid_fill(
     cp437_grid: *mut SPCp437Grid,
     value: u8,
 ) {
+    assert!(!cp437_grid.is_null());
     (*cp437_grid).0.fill(value);
 }
 
@@ -190,6 +217,10 @@ pub unsafe extern "C" fn sp_cp437_grid_fill(
 ///
 /// - `cp437_grid`: instance to read from
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -199,6 +230,7 @@ pub unsafe extern "C" fn sp_cp437_grid_fill(
 pub unsafe extern "C" fn sp_cp437_grid_width(
     cp437_grid: *const SPCp437Grid,
 ) -> usize {
+    assert!(!cp437_grid.is_null());
     (*cp437_grid).0.width()
 }
 
@@ -208,6 +240,10 @@ pub unsafe extern "C" fn sp_cp437_grid_width(
 ///
 /// - `cp437_grid`: instance to read from
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -217,6 +253,7 @@ pub unsafe extern "C" fn sp_cp437_grid_width(
 pub unsafe extern "C" fn sp_cp437_grid_height(
     cp437_grid: *const SPCp437Grid,
 ) -> usize {
+    assert!(!cp437_grid.is_null());
     (*cp437_grid).0.height()
 }
 
@@ -224,6 +261,10 @@ pub unsafe extern "C" fn sp_cp437_grid_height(
 ///
 /// Will never return NULL.
 ///
+/// # Panics
+///
+/// - when `cp437_grid` is NULL
+///
 /// ## Safety
 ///
 /// The caller has to make sure that:
diff --git a/crates/servicepoint_binding_c/src/packet.rs b/crates/servicepoint_binding_c/src/packet.rs
index ac27747..f2cffc4 100644
--- a/crates/servicepoint_binding_c/src/packet.rs
+++ b/crates/servicepoint_binding_c/src/packet.rs
@@ -14,6 +14,10 @@ pub struct SPPacket(pub(crate) servicepoint::packet::Packet);
 ///
 /// Will never return NULL.
 ///
+/// # Panics
+///
+/// - when `command` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -26,15 +30,22 @@ pub struct SPPacket(pub(crate) servicepoint::packet::Packet);
 pub unsafe extern "C" fn sp_packet_from_command(
     command: *mut SPCommand,
 ) -> *mut SPPacket {
+    assert!(!command.is_null());
     let command = *Box::from_raw(command);
     let packet = SPPacket(command.0.into());
-    Box::into_raw(Box::new(packet))
+    let result = Box::into_raw(Box::new(packet));
+    assert!(!result.is_null());
+    result
 }
 
 /// Tries to load a [SPPacket] from the passed array with the specified length.
 ///
 /// returns: NULL in case of an error, pointer to the allocated packet otherwise
 ///
+/// # Panics
+///
+/// - when `data` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -48,6 +59,7 @@ pub unsafe extern "C" fn sp_packet_try_load(
     data: *const u8,
     length: usize,
 ) -> *mut SPPacket {
+    assert!(!data.is_null());
     let data = std::slice::from_raw_parts(data, length);
     match servicepoint::packet::Packet::try_from(data) {
         Err(_) => null_mut(),
@@ -59,6 +71,10 @@ pub unsafe extern "C" fn sp_packet_try_load(
 ///
 /// Will never return NULL.
 ///
+/// # Panics
+///
+/// - when `packet` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -71,11 +87,18 @@ pub unsafe extern "C" fn sp_packet_try_load(
 pub unsafe extern "C" fn sp_packet_clone(
     packet: *const SPPacket,
 ) -> *mut SPPacket {
-    Box::into_raw(Box::new(SPPacket((*packet).0.clone())))
+    assert!(!packet.is_null());
+    let result = Box::into_raw(Box::new(SPPacket((*packet).0.clone())));
+    assert!(!result.is_null());
+    result
 }
 
 /// Deallocates a [SPPacket].
 ///
+/// # Panics
+///
+/// - when `sp_packet_free` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -84,5 +107,6 @@ pub unsafe extern "C" fn sp_packet_clone(
 /// - `packet` is not used concurrently or after this call
 #[no_mangle]
 pub unsafe extern "C" fn sp_packet_free(packet: *mut SPPacket) {
+    assert!(!packet.is_null());
     _ = Box::from_raw(packet)
 }
diff --git a/crates/servicepoint_binding_c/src/pixel_grid.rs b/crates/servicepoint_binding_c/src/pixel_grid.rs
index 6592ae5..8e937fc 100644
--- a/crates/servicepoint_binding_c/src/pixel_grid.rs
+++ b/crates/servicepoint_binding_c/src/pixel_grid.rs
@@ -42,9 +42,11 @@ pub unsafe extern "C" fn sp_pixel_grid_new(
     width: usize,
     height: usize,
 ) -> *mut SPPixelGrid {
-    Box::into_raw(Box::new(SPPixelGrid(servicepoint::PixelGrid::new(
+    let result = Box::into_raw(Box::new(SPPixelGrid(servicepoint::PixelGrid::new(
         width, height,
-    ))))
+    ))));
+    assert!(!result.is_null());
+    result
 }
 
 /// Loads a [SPPixelGrid] with the specified dimensions from the provided data.
@@ -58,6 +60,7 @@ pub unsafe extern "C" fn sp_pixel_grid_new(
 ///
 /// # Panics
 ///
+/// - when `data` is NULL
 /// - when the dimensions and data size do not match exactly.
 /// - when the width is not dividable by 8
 ///
@@ -75,16 +78,23 @@ pub unsafe extern "C" fn sp_pixel_grid_load(
     data: *const u8,
     data_length: usize,
 ) -> *mut SPPixelGrid {
+    assert!(!data.is_null());
     let data = std::slice::from_raw_parts(data, data_length);
-    Box::into_raw(Box::new(SPPixelGrid(servicepoint::PixelGrid::load(
+    let result = Box::into_raw(Box::new(SPPixelGrid(servicepoint::PixelGrid::load(
         width, height, data,
-    ))))
+    ))));
+    assert!(!result.is_null());
+    result
 }
 
 /// Clones a [SPPixelGrid].
 ///
 /// Will never return NULL.
 ///
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -97,11 +107,18 @@ pub unsafe extern "C" fn sp_pixel_grid_load(
 pub unsafe extern "C" fn sp_pixel_grid_clone(
     pixel_grid: *const SPPixelGrid,
 ) -> *mut SPPixelGrid {
-    Box::into_raw(Box::new(SPPixelGrid((*pixel_grid).0.clone())))
+    assert!(!pixel_grid.is_null());
+    let result = Box::into_raw(Box::new(SPPixelGrid((*pixel_grid).0.clone())));
+    assert!(!result.is_null());
+    result
 }
 
 /// Deallocates a [SPPixelGrid].
 ///
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -111,6 +128,7 @@ pub unsafe extern "C" fn sp_pixel_grid_clone(
 /// - `pixel_grid` was not passed to another consuming function, e.g. to create a [SPCommand]
 #[no_mangle]
 pub unsafe extern "C" fn sp_pixel_grid_free(pixel_grid: *mut SPPixelGrid) {
+    assert!(!pixel_grid.is_null());
     _ = Box::from_raw(pixel_grid);
 }
 
@@ -123,7 +141,8 @@ pub unsafe extern "C" fn sp_pixel_grid_free(pixel_grid: *mut SPPixelGrid) {
 ///
 /// # Panics
 ///
-/// When accessing `x` or `y` out of bounds.
+/// - when `pixel_grid` is NULL
+/// - when accessing `x` or `y` out of bounds
 ///
 /// # Safety
 ///
@@ -137,6 +156,7 @@ pub unsafe extern "C" fn sp_pixel_grid_get(
     x: usize,
     y: usize,
 ) -> bool {
+    assert!(!pixel_grid.is_null());
     (*pixel_grid).0.get(x, y)
 }
 
@@ -152,7 +172,8 @@ pub unsafe extern "C" fn sp_pixel_grid_get(
 ///
 /// # Panics
 ///
-/// When accessing `x` or `y` out of bounds.
+/// - when `pixel_grid` is NULL
+/// - when accessing `x` or `y` out of bounds
 ///
 /// # Safety
 ///
@@ -167,6 +188,7 @@ pub unsafe extern "C" fn sp_pixel_grid_set(
     y: usize,
     value: bool,
 ) {
+    assert!(!pixel_grid.is_null());
     (*pixel_grid).0.set(x, y, value);
 }
 
@@ -177,6 +199,10 @@ pub unsafe extern "C" fn sp_pixel_grid_set(
 /// - `pixel_grid`: instance to write to
 /// - `value`: the value to set all pixels to
 ///
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -188,6 +214,7 @@ pub unsafe extern "C" fn sp_pixel_grid_fill(
     pixel_grid: *mut SPPixelGrid,
     value: bool,
 ) {
+    assert!(!pixel_grid.is_null());
     (*pixel_grid).0.fill(value);
 }
 
@@ -197,6 +224,10 @@ pub unsafe extern "C" fn sp_pixel_grid_fill(
 ///
 /// - `pixel_grid`: instance to read from
 ///
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -206,6 +237,7 @@ pub unsafe extern "C" fn sp_pixel_grid_fill(
 pub unsafe extern "C" fn sp_pixel_grid_width(
     pixel_grid: *const SPPixelGrid,
 ) -> usize {
+    assert!(!pixel_grid.is_null());
     (*pixel_grid).0.width()
 }
 
@@ -215,6 +247,10 @@ pub unsafe extern "C" fn sp_pixel_grid_width(
 ///
 /// - `pixel_grid`: instance to read from
 ///
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
 /// # Safety
 ///
 /// The caller has to make sure that:
@@ -224,12 +260,17 @@ pub unsafe extern "C" fn sp_pixel_grid_width(
 pub unsafe extern "C" fn sp_pixel_grid_height(
     pixel_grid: *const SPPixelGrid,
 ) -> usize {
+    assert!(!pixel_grid.is_null());
     (*pixel_grid).0.height()
 }
 
 /// Gets an unsafe reference to the data of the [SPPixelGrid] instance.
 ///
-/// ## Safety
+/// # Panics
+///
+/// - when `pixel_grid` is NULL
+///
+/// # Safety
 ///
 /// The caller has to make sure that:
 ///
@@ -240,6 +281,7 @@ pub unsafe extern "C" fn sp_pixel_grid_height(
 pub unsafe extern "C" fn sp_pixel_grid_unsafe_data_ref(
     pixel_grid: *mut SPPixelGrid,
 ) -> SPByteSlice {
+    assert!(!pixel_grid.is_null());
     let data = (*pixel_grid).0.data_ref_mut();
     SPByteSlice {
         start: data.as_mut_ptr_range().start,