diff --git a/src/ir/var.rs b/src/ir/var.rs
index 0e7df61884..1c7b20280e 100644
--- a/src/ir/var.rs
+++ b/src/ir/var.rs
@@ -87,17 +87,19 @@ impl ClangSubItemParser for Var {
 
                 assert!(!id.is_empty(), "Empty macro name?");
 
-                if ctx.parsed_macro(&id) {
-                    let name = String::from_utf8(id).unwrap();
-                    warn!("Duplicated macro definition: {}", name);
-                    return Err(ParseError::Continue);
-                }
+                let previously_defined = ctx.parsed_macro(&id);
 
                 // NB: It's important to "note" the macro even if the result is
                 // not an integer, otherwise we might loose other kind of
                 // derived macros.
                 ctx.note_parsed_macro(id.clone(), value.clone());
 
+                if previously_defined {
+                    let name = String::from_utf8(id).unwrap();
+                    warn!("Duplicated macro definition: {}", name);
+                    return Err(ParseError::Continue);
+                }
+
                 // NOTE: Unwrapping, here and above, is safe, because the
                 // identifier of a token comes straight from clang, and we
                 // enforce utf8 there, so we should have already panicked at
diff --git a/tests/expectations/tests/macro-redef.rs b/tests/expectations/tests/macro-redef.rs
new file mode 100644
index 0000000000..881a44ae87
--- /dev/null
+++ b/tests/expectations/tests/macro-redef.rs
@@ -0,0 +1,9 @@
+/* automatically generated by rust-bindgen */
+
+
+#![allow(non_snake_case)]
+
+
+pub const FOO: ::std::os::raw::c_uint = 4;
+pub const BAR: ::std::os::raw::c_uint = 5;
+pub const BAZ: ::std::os::raw::c_uint = 6;
diff --git a/tests/headers/macro-redef.h b/tests/headers/macro-redef.h
new file mode 100644
index 0000000000..0180d2ab09
--- /dev/null
+++ b/tests/headers/macro-redef.h
@@ -0,0 +1,5 @@
+#define FOO 4
+#define BAR (1 + FOO)
+#undef FOO
+#define FOO 5
+#define BAZ (1 + FOO)