diff --git a/gio/Gir.toml b/gio/Gir.toml
index 7448735b816d..cfa9a751f01c 100644
--- a/gio/Gir.toml
+++ b/gio/Gir.toml
@@ -249,9 +249,9 @@ status = "generate"
     ignore = true
     [[object.function]]
     name = "content_type_guess"
-    # implemented manually until gir generates nullable array parameters
-    # https://github.com/gtk-rs/gir/issues/1133
-    manual = true
+        [[object.function.parameter]]
+        name = "filename"
+        string_type = "filename"
 
 [[object]]
 name = "Gio.ActionGroup"
diff --git a/gio/src/auto/functions.rs b/gio/src/auto/functions.rs
index 5a3df411f7dc..aeecbd2a3814 100644
--- a/gio/src/auto/functions.rs
+++ b/gio/src/auto/functions.rs
@@ -178,6 +178,24 @@ pub fn content_type_get_symbolic_icon(type_: &str) -> Icon {
     }
 }
 
+#[doc(alias = "g_content_type_guess")]
+pub fn content_type_guess(
+    filename: Option<impl AsRef<std::path::Path>>,
+    data: &[u8],
+) -> (glib::GString, bool) {
+    let data_size = data.len() as _;
+    unsafe {
+        let mut result_uncertain = std::mem::MaybeUninit::uninit();
+        let ret = from_glib_full(ffi::g_content_type_guess(
+            filename.as_ref().map(|p| p.as_ref()).to_glib_none().0,
+            data.to_glib_none().0,
+            data_size,
+            result_uncertain.as_mut_ptr(),
+        ));
+        (ret, from_glib(result_uncertain.assume_init()))
+    }
+}
+
 #[doc(alias = "g_content_type_guess_for_tree")]
 pub fn content_type_guess_for_tree(root: &impl IsA<File>) -> Vec<glib::GString> {
     unsafe {
diff --git a/gio/src/content_type.rs b/gio/src/content_type.rs
deleted file mode 100644
index 37a8d13bad08..000000000000
--- a/gio/src/content_type.rs
+++ /dev/null
@@ -1,26 +0,0 @@
-// Take a look at the license at the top of the repository in the LICENSE file.
-
-use std::ptr;
-
-use glib::translate::*;
-
-use crate::ffi;
-
-#[doc(alias = "g_content_type_guess")]
-pub fn content_type_guess<'a>(
-    filename: Option<impl AsRef<std::path::Path>>,
-    data: impl Into<Option<&'a [u8]>>,
-) -> (glib::GString, bool) {
-    let data = data.into();
-    let data_size = data.map_or(0, |d| d.len());
-    unsafe {
-        let mut result_uncertain = std::mem::MaybeUninit::uninit();
-        let ret = from_glib_full(ffi::g_content_type_guess(
-            filename.as_ref().map(|p| p.as_ref()).to_glib_none().0,
-            data.map_or(ptr::null(), |d| d.to_glib_none().0),
-            data_size,
-            result_uncertain.as_mut_ptr(),
-        ));
-        (ret, from_glib(result_uncertain.assume_init()))
-    }
-}
diff --git a/gio/src/lib.rs b/gio/src/lib.rs
index f11e3fb2338a..fd0765fa4a77 100644
--- a/gio/src/lib.rs
+++ b/gio/src/lib.rs
@@ -22,7 +22,6 @@ mod cancellable;
 pub use cancellable::CancelledHandlerId;
 mod cancellable_future;
 pub use crate::cancellable_future::{CancellableFuture, Cancelled};
-mod content_type;
 mod converter;
 mod credentials;
 mod data_input_stream;
@@ -117,7 +116,6 @@ pub mod builders {
 
 pub mod functions {
     pub use super::auto::functions::*;
-    pub use super::content_type::content_type_guess;
 }
 
 pub use crate::auto::*;
diff --git a/gio/tests/content_type.rs b/gio/tests/content_type.rs
deleted file mode 100644
index b05193430e72..000000000000
--- a/gio/tests/content_type.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-// Take a look at the license at the top of the repository in the LICENSE file.
-
-#[cfg(unix)]
-#[test]
-fn test_content_type_guess() {
-    // We only test for directory and file without extension here as we can't guarantee the
-    // CI runners will have any mimetypes installed.
-    let ret: (glib::GString, bool) =
-        gio::functions::content_type_guess(Some(std::path::Path::new("test/")), None);
-    assert_eq!(ret.0, "inode/directory");
-
-    let ret: (glib::GString, bool) =
-        gio::functions::content_type_guess(Some(std::path::Path::new("test")), None);
-    assert_eq!(ret.0, "application/octet-stream");
-}