diff --git a/libcc2rs/src/fn_ptr.rs b/libcc2rs/src/fn_ptr.rs
index 8aaf3d8a6..5611fd519 100644
--- a/libcc2rs/src/fn_ptr.rs
+++ b/libcc2rs/src/fn_ptr.rs
@@ -21,7 +21,7 @@ pub(crate) trait FnSig: Copy + 'static {
 
 macro_rules! impl_fn_sig {
     () => {
-        impl_fn_sig!(@gen A B C D E F G H I J K L M N O P);
+        impl_fn_sig!(@gen A B C D E F G H I J K L M N O P Q S T U V W X Y);
     };
     (@gen $($a:ident)*) => {
         impl<R: FnPtrArg $(, $a: FnPtrArg)*> FnSig for fn($($a,)*) -> R {
@@ -252,7 +252,7 @@ impl<T: FnSig> FnPtr<T> {
 // invokes, e.g. `fn_ptr.call(a0, a1)`.
 macro_rules! impl_fn_ptr_call {
     () => {
-        impl_fn_ptr_call!(@gen A B C D E F G H I J K L M N O P);
+        impl_fn_ptr_call!(@gen A B C D E F G H I J K L M N O P Q S T U V W X Y);
     };
     (@gen $($a:ident)*) => {
         impl<R: FnPtrArg $(, $a: FnPtrArg)*> FnPtr<fn($($a,)*) -> R> {
diff --git a/libcc2rs/src/fn_ptr_arg.rs b/libcc2rs/src/fn_ptr_arg.rs
index 6622c6ccd..621f8d27e 100644
--- a/libcc2rs/src/fn_ptr_arg.rs
+++ b/libcc2rs/src/fn_ptr_arg.rs
@@ -148,7 +148,7 @@ impl<T: ?Sized + 'static> FnPtrArg for *const T {
 
 macro_rules! impl_fn_ptr_arg_unsafe_fn {
     () => {
-        impl_fn_ptr_arg_unsafe_fn!(@gen A B C D E F G H I J K L M N O P);
+        impl_fn_ptr_arg_unsafe_fn!(@gen A B C D E F G H I J K L M N O P Q S T U V W X Y);
     };
     (@gen $($a:ident)*) => {
         impl<R: 'static $(, $a: 'static)*> FnPtrArg for Option<unsafe fn($($a,)*) -> R> {
@@ -224,7 +224,7 @@ pub(crate) trait FnPtrArgs: Sized + 'static {
 
 macro_rules! impl_fn_ptr_args {
     () => {
-        impl_fn_ptr_args!(@gen A B C D E F G H I J K L M N O P);
+        impl_fn_ptr_args!(@gen A B C D E F G H I J K L M N O P Q S T U V W X Y);
     };
     (@gen $($a:ident)*) => {
         impl_fn_ptr_args!(@arity $($a)*);
diff --git a/tests/unit/fn_ptr_arity.cpp b/tests/unit/fn_ptr_arity.cpp
index a3f3e7341..f940248cc 100644
--- a/tests/unit/fn_ptr_arity.cpp
+++ b/tests/unit/fn_ptr_arity.cpp
@@ -5,8 +5,23 @@ int foo(int a1, int a2, int a3, int a4, int a5, int a6, int a7, int a8, int a9,
   return 22;
 }
 
+int wide(int a1, int a2, int a3, int a4, int a5, int a6, int a7, int a8, int a9,
+         int a10, int a11, int a12, int a13, int a14, int a15, int a16, int a17,
+         int a18, int a19, int a20, int a21, int a22) {
+  return a1 + a22;
+}
+
 int main() {
   auto f = &foo;
   assert(f(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14) == 22);
+
+  auto w = &wide;
+  assert(w(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
+           20, 21, 22) == 23);
+
+  auto l = [](int a1, int a2, int a3, int a4, int a5, int a6, int a7, int a8,
+              int a9, int a10, int a11, int a12, int a13, int a14, int a15,
+              int a16, int a17, int a18) { return a1 * a18; };
+  assert(l(2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9) == 18);
   return 0;
 }
diff --git a/tests/unit/out/refcount/fn_ptr_arity.rs b/tests/unit/out/refcount/fn_ptr_arity.rs
index e2f3d1c93..6868ede7e 100644
--- a/tests/unit/out/refcount/fn_ptr_arity.rs
+++ b/tests/unit/out/refcount/fn_ptr_arity.rs
@@ -24,6 +24,32 @@ pub fn foo_0(
 ) -> i32 {
     return 22;
 }
+pub fn wide_1(
+    mut a1: i32,
+    mut a2: i32,
+    mut a3: i32,
+    mut a4: i32,
+    mut a5: i32,
+    mut a6: i32,
+    mut a7: i32,
+    mut a8: i32,
+    mut a9: i32,
+    mut a10: i32,
+    mut a11: i32,
+    mut a12: i32,
+    mut a13: i32,
+    mut a14: i32,
+    mut a15: i32,
+    mut a16: i32,
+    mut a17: i32,
+    mut a18: i32,
+    mut a19: i32,
+    mut a20: i32,
+    mut a21: i32,
+    mut a22: i32,
+) -> i32 {
+    return (a1 + a22);
+}
 pub fn main() {
     __cpp2rust_init_globals();
     std::process::exit(main_0());
@@ -31,6 +57,136 @@ pub fn main() {
 fn main_0() -> i32 {
     let mut f : FnPtr<fn(i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,) -> i32  >  = ( FnPtr::<fn(i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,i32  ,) -> i32  >::new(foo_0)  )  ;
     assert!((({ f.call(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,) }) == 22));
+    let mut w: FnPtr<
+        fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    > = (FnPtr::<
+        fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    >::new(wide_1));
+    assert!(
+        (({
+            w.call(
+                1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
+            )
+        }) == 23)
+    );
+    let l: Value<
+        FnPtr<
+            fn(
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+                i32,
+            ) -> i32,
+        >,
+    > = Rc::new(RefCell::new(FnPtr::<
+        fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    >::new(
+        |a1: i32,
+         a2: i32,
+         a3: i32,
+         a4: i32,
+         a5: i32,
+         a6: i32,
+         a7: i32,
+         a8: i32,
+         a9: i32,
+         a10: i32,
+         a11: i32,
+         a12: i32,
+         a13: i32,
+         a14: i32,
+         a15: i32,
+         a16: i32,
+         a17: i32,
+         a18: i32|
+         -> i32 {
+            {
+                return (a1 * a18);
+            }
+        },
+    )));
+    assert!(
+        (({ (*l.borrow()).call(2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9,) }) == 18)
+    );
     return 0;
 }
 pub fn __cpp2rust_init_globals() {}
diff --git a/tests/unit/out/unsafe/fn_ptr_arity.rs b/tests/unit/out/unsafe/fn_ptr_arity.rs
index 64d49e907..d73f56648 100644
--- a/tests/unit/out/unsafe/fn_ptr_arity.rs
+++ b/tests/unit/out/unsafe/fn_ptr_arity.rs
@@ -24,6 +24,32 @@ pub unsafe fn foo_0(
 ) -> i32 {
     return 22;
 }
+pub unsafe fn wide_1(
+    mut a1: i32,
+    mut a2: i32,
+    mut a3: i32,
+    mut a4: i32,
+    mut a5: i32,
+    mut a6: i32,
+    mut a7: i32,
+    mut a8: i32,
+    mut a9: i32,
+    mut a10: i32,
+    mut a11: i32,
+    mut a12: i32,
+    mut a13: i32,
+    mut a14: i32,
+    mut a15: i32,
+    mut a16: i32,
+    mut a17: i32,
+    mut a18: i32,
+    mut a19: i32,
+    mut a20: i32,
+    mut a21: i32,
+    mut a22: i32,
+) -> i32 {
+    return ((a1) + (a22));
+}
 pub fn main() {
     unsafe {
         __cpp2rust_init_globals();
@@ -35,6 +61,107 @@ unsafe fn main_0() -> i32 {
         unsafe fn(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) -> i32,
     > = (Some(foo_0));
     assert!(((unsafe { (f).unwrap()(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,) }) == (22)));
+    let mut w: Option<
+        unsafe fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    > = (Some(wide_1));
+    assert!(
+        ((unsafe {
+            (w).unwrap()(
+                1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
+            )
+        }) == (23))
+    );
+    let mut l: FnPtr<
+        fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    > = FnPtr::<
+        fn(
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+            i32,
+        ) -> i32,
+    >::new(
+        |a1: i32,
+         a2: i32,
+         a3: i32,
+         a4: i32,
+         a5: i32,
+         a6: i32,
+         a7: i32,
+         a8: i32,
+         a9: i32,
+         a10: i32,
+         a11: i32,
+         a12: i32,
+         a13: i32,
+         a14: i32,
+         a15: i32,
+         a16: i32,
+         a17: i32,
+         a18: i32|
+         -> i32 {
+            unsafe {
+                return ((a1) * (a18));
+            }
+        },
+    );
+    assert!(((unsafe { l.call(2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9,) }) == (18)));
     return 0;
 }
 pub unsafe fn __cpp2rust_init_globals() {}