diff --git a/src/bindgen/ir/documentation.rs b/src/bindgen/ir/documentation.rs
index 1a6b318d2..53da91667 100644
--- a/src/bindgen/ir/documentation.rs
+++ b/src/bindgen/ir/documentation.rs
@@ -26,6 +26,12 @@ impl Documentation {
         Documentation { doc_comment: doc }
     }
 
+    pub fn simple(line: &str) -> Self {
+        Documentation {
+            doc_comment: vec![line.to_owned()],
+        }
+    }
+
     pub fn none() -> Self {
         Documentation {
             doc_comment: Vec::new(),
diff --git a/src/bindgen/ir/enumeration.rs b/src/bindgen/ir/enumeration.rs
index 46ab4c27a..71d0c0eb3 100644
--- a/src/bindgen/ir/enumeration.rs
+++ b/src/bindgen/ir/enumeration.rs
@@ -253,7 +253,11 @@ impl Enum {
         }
     }
 
-    pub fn load(item: &syn::ItemEnum, mod_cfg: Option<&Cfg>) -> Result<Enum, String> {
+    pub fn load(
+        item: &syn::ItemEnum,
+        mod_cfg: Option<&Cfg>,
+        config: &Config,
+    ) -> Result<Enum, String> {
         let repr = Repr::load(&item.attrs)?;
         if repr.style == ReprStyle::Rust && repr.ty.is_none() {
             return Err("Enum is not marked with a valid #[repr(prim)] or #[repr(C)].".to_owned());
@@ -289,6 +293,15 @@ impl Enum {
             }
         }
 
+        if config.enumeration.add_sentinel(&annotations) {
+            variants.push(EnumVariant::new(
+                "Sentinel".to_owned(),
+                None,
+                None,
+                Documentation::simple(" Must be last for serialization purposes"),
+            ));
+        }
+
         let tag = if is_tagged {
             Some("Tag".to_string())
         } else {
@@ -596,11 +609,6 @@ impl Source for Enum {
             }
             variant.write(config, out);
         }
-        if config.enumeration.add_sentinel(&self.annotations) {
-            out.new_line();
-            out.new_line();
-            out.write("Sentinel /* this must be last for serialization purposes. */");
-        }
 
         if config.language == Language::C && size.is_none() && config.style.generate_typedef() {
             out.close_brace(false);
diff --git a/src/bindgen/parser.rs b/src/bindgen/parser.rs
index 1a36722a4..f514fe74b 100644
--- a/src/bindgen/parser.rs
+++ b/src/bindgen/parser.rs
@@ -452,7 +452,7 @@ impl Parse {
                     self.load_syn_union(config, crate_name, mod_cfg, item);
                 }
                 syn::Item::Enum(ref item) => {
-                    self.load_syn_enum(crate_name, mod_cfg, item);
+                    self.load_syn_enum(config, crate_name, mod_cfg, item);
                 }
                 syn::Item::Type(ref item) => {
                     self.load_syn_ty(crate_name, mod_cfg, item);
@@ -860,7 +860,13 @@ impl Parse {
     }
 
     /// Loads a `enum` declaration
-    fn load_syn_enum(&mut self, crate_name: &str, mod_cfg: Option<&Cfg>, item: &syn::ItemEnum) {
+    fn load_syn_enum(
+        &mut self,
+        config: &Config,
+        crate_name: &str,
+        mod_cfg: Option<&Cfg>,
+        item: &syn::ItemEnum,
+    ) {
         if item.generics.lifetimes().count() > 0 {
             info!(
                 "Skip {}::{} - (has generics or lifetimes or where bounds).",
@@ -869,7 +875,7 @@ impl Parse {
             return;
         }
 
-        match Enum::load(item, mod_cfg) {
+        match Enum::load(item, mod_cfg, config) {
             Ok(en) => {
                 info!("Take {}::{}.", crate_name, &item.ident);
                 self.enums.try_insert(en);
diff --git a/tests/expectations/both/sentinel.c b/tests/expectations/both/sentinel.c
new file mode 100644
index 000000000..f7a45c938
--- /dev/null
+++ b/tests/expectations/both/sentinel.c
@@ -0,0 +1,55 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+typedef uint8_t A;
+
+enum B {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+typedef uint8_t B;
+
+enum C_Tag {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+typedef uint8_t C_Tag;
+
+typedef struct C_C1_Body {
+  C_Tag tag;
+  uint32_t a;
+} C_C1_Body;
+
+typedef struct C_C2_Body {
+  C_Tag tag;
+  uint32_t b;
+} C_C2_Body;
+
+typedef union C {
+  C_Tag tag;
+  C_C1_Body c1;
+  C_C2_Body c2;
+} C;
+
+void root(A a, B b, C c);
diff --git a/tests/expectations/both/sentinel.compat.c b/tests/expectations/both/sentinel.compat.c
new file mode 100644
index 000000000..95b1e0697
--- /dev/null
+++ b/tests/expectations/both/sentinel.compat.c
@@ -0,0 +1,81 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t A;
+#endif // __cplusplus
+
+enum B
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t B;
+#endif // __cplusplus
+
+enum C_Tag
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t C_Tag;
+#endif // __cplusplus
+
+typedef struct C_C1_Body {
+  C_Tag tag;
+  uint32_t a;
+} C_C1_Body;
+
+typedef struct C_C2_Body {
+  C_Tag tag;
+  uint32_t b;
+} C_C2_Body;
+
+typedef union C {
+  C_Tag tag;
+  C_C1_Body c1;
+  C_C2_Body c2;
+} C;
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+void root(A a, B b, C c);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
diff --git a/tests/expectations/sentinel.c b/tests/expectations/sentinel.c
new file mode 100644
index 000000000..27057f3aa
--- /dev/null
+++ b/tests/expectations/sentinel.c
@@ -0,0 +1,55 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+typedef uint8_t A;
+
+enum B {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+typedef uint8_t B;
+
+enum C_Tag {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+typedef uint8_t C_Tag;
+
+typedef struct {
+  C_Tag tag;
+  uint32_t a;
+} C_C1_Body;
+
+typedef struct {
+  C_Tag tag;
+  uint32_t b;
+} C_C2_Body;
+
+typedef union {
+  C_Tag tag;
+  C_C1_Body c1;
+  C_C2_Body c2;
+} C;
+
+void root(A a, B b, C c);
diff --git a/tests/expectations/sentinel.compat.c b/tests/expectations/sentinel.compat.c
new file mode 100644
index 000000000..e86d2d934
--- /dev/null
+++ b/tests/expectations/sentinel.compat.c
@@ -0,0 +1,81 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t A;
+#endif // __cplusplus
+
+enum B
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t B;
+#endif // __cplusplus
+
+enum C_Tag
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t C_Tag;
+#endif // __cplusplus
+
+typedef struct {
+  C_Tag tag;
+  uint32_t a;
+} C_C1_Body;
+
+typedef struct {
+  C_Tag tag;
+  uint32_t b;
+} C_C2_Body;
+
+typedef union {
+  C_Tag tag;
+  C_C1_Body c1;
+  C_C2_Body c2;
+} C;
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+void root(A a, B b, C c);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
diff --git a/tests/expectations/sentinel.cpp b/tests/expectations/sentinel.cpp
new file mode 100644
index 000000000..316d1ce0d
--- /dev/null
+++ b/tests/expectations/sentinel.cpp
@@ -0,0 +1,52 @@
+#include <cstdarg>
+#include <cstdint>
+#include <cstdlib>
+#include <new>
+
+enum class A : uint8_t {
+  A_A1,
+  A_A2,
+  A_A3,
+  /// Must be last for serialization purposes
+  A_Sentinel,
+};
+
+enum class B : uint8_t {
+  B_B1,
+  B_B2,
+  B_B3,
+  /// Must be last for serialization purposes
+  B_Sentinel,
+};
+
+union C {
+  enum class Tag : uint8_t {
+    C_C1,
+    C_C2,
+    C_C3,
+    /// Must be last for serialization purposes
+    C_Sentinel,
+  };
+
+  struct C_C1_Body {
+    Tag tag;
+    uint32_t a;
+  };
+
+  struct C_C2_Body {
+    Tag tag;
+    uint32_t b;
+  };
+
+  struct {
+    Tag tag;
+  };
+  C_C1_Body c1;
+  C_C2_Body c2;
+};
+
+extern "C" {
+
+void root(A a, B b, C c);
+
+} // extern "C"
diff --git a/tests/expectations/tag/sentinel.c b/tests/expectations/tag/sentinel.c
new file mode 100644
index 000000000..684eeb3eb
--- /dev/null
+++ b/tests/expectations/tag/sentinel.c
@@ -0,0 +1,55 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+typedef uint8_t A;
+
+enum B {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+typedef uint8_t B;
+
+enum C_Tag {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+typedef uint8_t C_Tag;
+
+struct C_C1_Body {
+  C_Tag tag;
+  uint32_t a;
+};
+
+struct C_C2_Body {
+  C_Tag tag;
+  uint32_t b;
+};
+
+union C {
+  enum C_Tag tag;
+  struct C_C1_Body c1;
+  struct C_C2_Body c2;
+};
+
+void root(A a, B b, union C c);
diff --git a/tests/expectations/tag/sentinel.compat.c b/tests/expectations/tag/sentinel.compat.c
new file mode 100644
index 000000000..828bbcc46
--- /dev/null
+++ b/tests/expectations/tag/sentinel.compat.c
@@ -0,0 +1,81 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+enum A
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  A_A1,
+  A_A2,
+  A_A3,
+  /**
+   * Must be last for serialization purposes
+   */
+  A_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t A;
+#endif // __cplusplus
+
+enum B
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  B_B1,
+  B_B2,
+  B_B3,
+  /**
+   * Must be last for serialization purposes
+   */
+  B_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t B;
+#endif // __cplusplus
+
+enum C_Tag
+#ifdef __cplusplus
+  : uint8_t
+#endif // __cplusplus
+ {
+  C_C1,
+  C_C2,
+  C_C3,
+  /**
+   * Must be last for serialization purposes
+   */
+  C_Sentinel,
+};
+#ifndef __cplusplus
+typedef uint8_t C_Tag;
+#endif // __cplusplus
+
+struct C_C1_Body {
+  C_Tag tag;
+  uint32_t a;
+};
+
+struct C_C2_Body {
+  C_Tag tag;
+  uint32_t b;
+};
+
+union C {
+  enum C_Tag tag;
+  struct C_C1_Body c1;
+  struct C_C2_Body c2;
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+void root(A a, B b, union C c);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
diff --git a/tests/rust/sentinel.rs b/tests/rust/sentinel.rs
new file mode 100644
index 000000000..601b6ee62
--- /dev/null
+++ b/tests/rust/sentinel.rs
@@ -0,0 +1,23 @@
+#[repr(u8)]
+pub enum A {
+    A1,
+    A2,
+    A3,
+}
+
+#[repr(u8)]
+pub enum B {
+    B1,
+    B2,
+    B3,
+}
+
+#[repr(u8)]
+pub enum C {
+    C1 { a: u32 },
+    C2 { b: u32 },
+    C3,
+}
+
+#[no_mangle]
+pub extern "C" fn root(a: A, b: B, c: C) {}
diff --git a/tests/rust/sentinel.toml b/tests/rust/sentinel.toml
new file mode 100644
index 000000000..281803f97
--- /dev/null
+++ b/tests/rust/sentinel.toml
@@ -0,0 +1,3 @@
+[enum]
+add_sentinel = true
+prefix_with_name = true