diff --git a/lib/runtime-c-api/build.rs b/lib/runtime-c-api/build.rs
index 1978c9934..7750b0081 100644
--- a/lib/runtime-c-api/build.rs
+++ b/lib/runtime-c-api/build.rs
@@ -14,19 +14,21 @@ fn main() {
 
     const WASMER_PRE_HEADER: &str = r#"
 #if !defined(WASMER_H_MACROS)
-  #define WASMER_H_MACROS
-  #if defined(MSVC)
-    #if defined(_M_AMD64)
-      #define ARCH_X86_64
-    #endif
-  #endif
+#define WASMER_H_MACROS
 
-  #if defined(GCC) || defined(__clang__)
-    #if defined(__x86_64__)
-      #define ARCH_X86_64
-    #endif
-  #endif
+#if defined(MSVC)
+#if defined(_M_AMD64)
+#define ARCH_X86_64
 #endif
+#endif
+
+#if defined(GCC) || defined(__clang__)
+#if defined(__x86_64__)
+#define ARCH_X86_64
+#endif
+#endif
+
+#endif // WASMER_H_MACROS
 "#;
     // Generate the C bindings in the `OUT_DIR`.
     out_wasmer_header_file.set_extension("h");