diff --git a/src/lib.rs b/src/lib.rs
index e3a2b98b0..527d1d67d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1311,6 +1311,13 @@ impl Build {
         if self.cuda && self.files.len() > 1 {
             cmd.arg("--device-c");
         }
+        if compiler.family == (ToolFamily::Msvc { clang_cl: true }) {
+            // #513: For `clang-cl`, separate flags/options from the input file.
+            // When cross-compiling macOS -> Windows, this avoids interpreting
+            // common `/Users/...` paths as the `/U` flag and triggering
+            // `-Wslash-u-filename` warning.
+            cmd.arg("--");
+        }
         cmd.arg(&obj.src);
         if cfg!(target_os = "macos") {
             self.fix_env_for_apple_os(&mut cmd)?;
diff --git a/tests/test.rs b/tests/test.rs
index 3c9b4dc49..35ef87577 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -343,6 +343,14 @@ fn gnu_static() {
     test.cmd(0).must_have("-static").must_not_have("-shared");
 }
 
+#[test]
+fn gnu_no_dash_dash() {
+    let test = Test::gnu();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("--");
+}
+
 #[test]
 fn msvc_smoke() {
     reset_env();
@@ -411,3 +419,11 @@ fn msvc_no_static_crt() {
 
     test.cmd(0).must_have("-MD");
 }
+
+#[test]
+fn msvc_no_dash_dash() {
+    let test = Test::msvc();
+    test.gcc().file("foo.c").compile("foo");
+
+    test.cmd(0).must_not_have("--");
+}