diff --git a/syntax/check.rs b/syntax/check.rs
index 7e368f4..9aaf738 100644
--- a/syntax/check.rs
+++ b/syntax/check.rs
@@ -147,10 +147,6 @@
 }
 
 fn check_type_ref(cx: &mut Check, ty: &Ref) {
-    if ty.lifetime.is_some() {
-        cx.error(ty, "references with explicit lifetimes are not supported");
-    }
-
     if ty.mutability.is_some() && !ty.pinned {
         if let Some(requires_pin) = match &ty.inner {
             Type::Ident(ident) if ident.rust == CxxString || is_opaque_cxx(cx, &ident.rust) => {
@@ -249,6 +245,25 @@
 }
 
 fn check_api_fn(cx: &mut Check, efn: &ExternFn) {
+    match efn.lang {
+        Lang::Cxx => {
+            if !efn.generics.params.is_empty() && !efn.trusted {
+                let ref span = span_for_generics_error(efn);
+                cx.error(span, "extern C++ function with lifetimes must be declared in `unsafe extern \"C++\"` block");
+            }
+        }
+        Lang::Rust => {
+            if !efn.generics.params.is_empty() && efn.unsafety.is_none() {
+                let ref span = span_for_generics_error(efn);
+                let message = format!(
+                    "must be `unsafe fn {}` in order to expose explicit lifetimes to C++",
+                    efn.name.rust,
+                );
+                cx.error(span, message);
+            }
+        }
+    }
+
     if let Some(receiver) = &efn.receiver {
         let ref span = span_for_receiver_error(receiver);
 
@@ -281,10 +296,6 @@
                 ),
             );
         }
-
-        if receiver.lifetime.is_some() {
-            cx.error(span, "references with explicit lifetimes are not supported");
-        }
     }
 
     for arg in &efn.args {
@@ -436,6 +447,13 @@
     }
 }
 
+fn span_for_generics_error(efn: &ExternFn) -> TokenStream {
+    let unsafety = efn.unsafety;
+    let fn_token = efn.fn_token;
+    let generics = &efn.generics;
+    quote!(#unsafety #fn_token #generics)
+}
+
 fn describe(cx: &mut Check, ty: &Type) -> String {
     match ty {
         Type::Ident(ident) => {