diff --git a/boring-sys/build/main.rs b/boring-sys/build/main.rs
index 0f7053cb..35d5bd24 100644
--- a/boring-sys/build/main.rs
+++ b/boring-sys/build/main.rs
@@ -658,15 +658,15 @@ fn generate_bindings(config: &Config) {
             .clang_arg("--sysroot")
             .clang_arg(sysroot.display().to_string());
 
-        let c_target = format!(
-            "{}-{}-{}",
-            &config.target_arch, &config.target_os, &config.target_env
-        );
-
         // we need to add special platform header file with env for support cross building
-        let header = format!("{}/usr/include/{}", sysroot.display(), c_target);
-        if PathBuf::from(&header).is_dir() {
-            builder = builder.clang_arg("-I").clang_arg(&header);
+        let target_include_dir = sysroot.join(format!(
+            "usr/include/{}-{}-{}",
+            config.target_arch, config.target_os, config.target_env
+        ));
+        if target_include_dir.is_dir() {
+            builder = builder
+                .clang_arg("-I")
+                .clang_arg(target_include_dir.display().to_string());
         }
     }