diff --git a/src/codegen/mod.rs b/src/codegen/mod.rs
index a0b26eadb6..3f7c87e84d 100755
--- a/src/codegen/mod.rs
+++ b/src/codegen/mod.rs
@@ -1930,8 +1930,10 @@ mod utils {
     pub fn prepend_union_types(ctx: &BindgenContext,
                                result: &mut Vec<P<ast::Item>>) {
         let prefix = ctx.trait_prefix();
+
+        // TODO(emilio): The fmt::Debug impl could be way nicer with
+        // std::intrinsics::type_name, but...
         let union_field_decl = quote_item!(ctx.ext_cx(),
-            #[derive(Debug)]
             #[repr(C)]
             pub struct __BindgenUnionField<T>(
                 ::$prefix::marker::PhantomData<T>);
@@ -1983,11 +1985,22 @@ mod utils {
         )
             .unwrap();
 
+        let union_field_debug_impl = quote_item!(ctx.ext_cx(),
+            impl<T> ::std::fmt::Debug for __BindgenUnionField<T> {
+                fn fmt(&self, fmt: &mut ::std::fmt::Formatter)
+                       -> ::std::fmt::Result {
+                    fmt.write_str("__BindgenUnionField")
+                }
+            }
+        )
+            .unwrap();
+
         let items = vec![
             union_field_decl, union_field_impl,
             union_field_default_impl,
             union_field_clone_impl,
             union_field_copy_impl,
+            union_field_debug_impl,
         ];
 
         let old_items = mem::replace(result, items);
diff --git a/tests/expectations/tests/anon_union.rs b/tests/expectations/tests/anon_union.rs
index 0b1da364a2..8af416c32c 100644
--- a/tests/expectations/tests/anon_union.rs
+++ b/tests/expectations/tests/anon_union.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy, Clone)]
 pub struct TErrorResult<T> {
diff --git a/tests/expectations/tests/class.rs b/tests/expectations/tests/class.rs
index 4f736342e6..579c24a44b 100644
--- a/tests/expectations/tests/class.rs
+++ b/tests/expectations/tests/class.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 pub struct C {
     pub a: ::std::os::raw::c_int,
diff --git a/tests/expectations/tests/class_with_inner_struct.rs b/tests/expectations/tests/class_with_inner_struct.rs
index ca8eb73b09..ab51396dbf 100644
--- a/tests/expectations/tests/class_with_inner_struct.rs
+++ b/tests/expectations/tests/class_with_inner_struct.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct A {
diff --git a/tests/expectations/tests/jsval_layout_opaque.rs b/tests/expectations/tests/jsval_layout_opaque.rs
index fa611f2045..91f898af88 100644
--- a/tests/expectations/tests/jsval_layout_opaque.rs
+++ b/tests/expectations/tests/jsval_layout_opaque.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 pub const JSVAL_TAG_SHIFT: ::std::os::raw::c_uint = 47;
 pub const JSVAL_PAYLOAD_MASK: ::std::os::raw::c_ulonglong = 140737488355327;
 pub const JSVAL_TAG_MASK: ::std::os::raw::c_longlong = -140737488355328;
diff --git a/tests/expectations/tests/struct_with_anon_union.rs b/tests/expectations/tests/struct_with_anon_union.rs
index 7c4a7d82d4..0d2e937ac3 100644
--- a/tests/expectations/tests/struct_with_anon_union.rs
+++ b/tests/expectations/tests/struct_with_anon_union.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/struct_with_anon_unnamed_union.rs b/tests/expectations/tests/struct_with_anon_unnamed_union.rs
index 0763f5907a..2914eb41ff 100644
--- a/tests/expectations/tests/struct_with_anon_unnamed_union.rs
+++ b/tests/expectations/tests/struct_with_anon_unnamed_union.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/struct_with_nesting.rs b/tests/expectations/tests/struct_with_nesting.rs
index 0aacb6b3d3..97a0949ea2 100644
--- a/tests/expectations/tests/struct_with_nesting.rs
+++ b/tests/expectations/tests/struct_with_nesting.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/typeref.rs b/tests/expectations/tests/typeref.rs
index a8fe14cdbe..da9441462c 100644
--- a/tests/expectations/tests/typeref.rs
+++ b/tests/expectations/tests/typeref.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct nsFoo {
diff --git a/tests/expectations/tests/union_dtor.rs b/tests/expectations/tests/union_dtor.rs
index 4d1fa25a38..9be626ffa8 100644
--- a/tests/expectations/tests/union_dtor.rs
+++ b/tests/expectations/tests/union_dtor.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug)]
 pub struct UnionWithDtor {
diff --git a/tests/expectations/tests/union_fields.rs b/tests/expectations/tests/union_fields.rs
index 49bdca13b3..495e80f984 100644
--- a/tests/expectations/tests/union_fields.rs
+++ b/tests/expectations/tests/union_fields.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct _bindgen_ty_1 {
diff --git a/tests/expectations/tests/union_template.rs b/tests/expectations/tests/union_template.rs
index 0114e30663..fc92afb83e 100644
--- a/tests/expectations/tests/union_template.rs
+++ b/tests/expectations/tests/union_template.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy, Clone)]
 pub struct NastyStruct<T> {
diff --git a/tests/expectations/tests/union_with_anon_struct.rs b/tests/expectations/tests/union_with_anon_struct.rs
index 406dd231ed..f0a2151223 100644
--- a/tests/expectations/tests/union_with_anon_struct.rs
+++ b/tests/expectations/tests/union_with_anon_struct.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/union_with_anon_struct_bitfield.rs b/tests/expectations/tests/union_with_anon_struct_bitfield.rs
index 91d9fa5974..548b0dc48a 100644
--- a/tests/expectations/tests/union_with_anon_struct_bitfield.rs
+++ b/tests/expectations/tests/union_with_anon_struct_bitfield.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/union_with_anon_union.rs b/tests/expectations/tests/union_with_anon_union.rs
index c7ca3411c6..9527855640 100644
--- a/tests/expectations/tests/union_with_anon_union.rs
+++ b/tests/expectations/tests/union_with_anon_union.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/union_with_anon_unnamed_struct.rs b/tests/expectations/tests/union_with_anon_unnamed_struct.rs
index 33d75affb6..2d6fab97b7 100644
--- a/tests/expectations/tests/union_with_anon_unnamed_struct.rs
+++ b/tests/expectations/tests/union_with_anon_unnamed_struct.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct pixel {
diff --git a/tests/expectations/tests/union_with_anon_unnamed_union.rs b/tests/expectations/tests/union_with_anon_unnamed_union.rs
index c47850f59e..eb214017fe 100644
--- a/tests/expectations/tests/union_with_anon_unnamed_union.rs
+++ b/tests/expectations/tests/union_with_anon_unnamed_union.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/expectations/tests/union_with_big_member.rs b/tests/expectations/tests/union_with_big_member.rs
index 521a5ff4c7..b921f33c95 100644
--- a/tests/expectations/tests/union_with_big_member.rs
+++ b/tests/expectations/tests/union_with_big_member.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Copy)]
 pub struct WithBigArray {
@@ -40,6 +44,21 @@ impl Clone for WithBigArray {
     fn clone(&self) -> Self { *self }
 }
 #[repr(C)]
+#[derive(Debug, Copy)]
+pub struct WithBigArray2 {
+    pub a: __BindgenUnionField<::std::os::raw::c_int>,
+    pub b: __BindgenUnionField<[::std::os::raw::c_char; 33usize]>,
+    pub bindgen_union_field: [u32; 9usize],
+}
+#[test]
+fn bindgen_test_layout_WithBigArray2() {
+    assert_eq!(::std::mem::size_of::<WithBigArray2>() , 36usize);
+    assert_eq!(::std::mem::align_of::<WithBigArray2>() , 4usize);
+}
+impl Clone for WithBigArray2 {
+    fn clone(&self) -> Self { *self }
+}
+#[repr(C)]
 #[derive(Copy)]
 pub struct WithBigMember {
     pub a: __BindgenUnionField<::std::os::raw::c_int>,
diff --git a/tests/expectations/tests/union_with_nesting.rs b/tests/expectations/tests/union_with_nesting.rs
index 6ed81adb49..61c08a2a3e 100644
--- a/tests/expectations/tests/union_with_nesting.rs
+++ b/tests/expectations/tests/union_with_nesting.rs
@@ -4,7 +4,6 @@
 #![allow(non_snake_case)]
 
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct __BindgenUnionField<T>(::std::marker::PhantomData<T>);
 impl <T> __BindgenUnionField<T> {
@@ -24,6 +23,11 @@ impl <T> ::std::clone::Clone for __BindgenUnionField<T> {
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __BindgenUnionField<T> { }
+impl <T> ::std::fmt::Debug for __BindgenUnionField<T> {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+        fmt.write_str("__BindgenUnionField")
+    }
+}
 #[repr(C)]
 #[derive(Debug, Copy)]
 pub struct foo {
diff --git a/tests/headers/union_with_big_member.h b/tests/headers/union_with_big_member.h
index 06682ef191..6347d6cad3 100644
--- a/tests/headers/union_with_big_member.h
+++ b/tests/headers/union_with_big_member.h
@@ -3,6 +3,11 @@ union WithBigArray {
   int b[33];
 };
 
+union WithBigArray2 {
+  int a;
+  char b[33];
+};
+
 union WithBigMember {
   int a;
   union WithBigArray b;