diff --git a/r2r_common/src/lib.rs b/r2r_common/src/lib.rs
index ebd3d015e..be6e57acd 100644
--- a/r2r_common/src/lib.rs
+++ b/r2r_common/src/lib.rs
@@ -63,19 +63,19 @@ pub fn setup_bindgen_builder() -> bindgen::Builder {
         }
 
         let ament_prefix_var_name = "AMENT_PREFIX_PATH";
+        let split_char = if cfg!(target_os = "windows") {
+            ';'
+        } else {
+            ':'
+        };
         let ament_prefix_var = {
             let mut ament_str = env::var_os(ament_prefix_var_name).expect("Source your ROS!");
             if let Some(cmake_prefix_var) = env::var_os("CMAKE_PREFIX_PATH") {
-                ament_str.push(";");
+                ament_str.push(&split_char.to_string());
                 ament_str.push(cmake_prefix_var);
             }
             RawOsString::new(ament_str)
         };
-        let split_char = if cfg!(target_os = "windows") {
-            ';'
-        } else {
-            ':'
-        };
         for p in ament_prefix_var.split(split_char) {
             let path = Path::new(&p.to_os_str()).join("include");