diff --git a/crates/proc_macro_srv/src/abis/abi_1_55/rustc_server.rs b/crates/proc_macro_srv/src/abis/abi_1_55/rustc_server.rs
index f8626c5f62f..6105238d0b2 100644
--- a/crates/proc_macro_srv/src/abis/abi_1_55/rustc_server.rs
+++ b/crates/proc_macro_srv/src/abis/abi_1_55/rustc_server.rs
@@ -488,8 +488,8 @@ fn debug_kind(&mut self, _literal: &Self::Literal) -> String {
         // They must still be present to be ABI-compatible and work with upstream proc_macro.
         "".to_owned()
     }
-    fn from_str(&mut self, _s: &str) -> Result<Self::Literal, ()> {
-        unimplemented!()
+    fn from_str(&mut self, s: &str) -> Result<Self::Literal, ()> {
+        Ok(Literal { text: s.into(), id: tt::TokenId::unspecified() })
     }
     fn symbol(&mut self, literal: &Self::Literal) -> String {
         literal.text.to_string()
diff --git a/crates/proc_macro_srv/src/abis/abi_1_56/rustc_server.rs b/crates/proc_macro_srv/src/abis/abi_1_56/rustc_server.rs
index fb8a4c8cbe8..1cebc289f8a 100644
--- a/crates/proc_macro_srv/src/abis/abi_1_56/rustc_server.rs
+++ b/crates/proc_macro_srv/src/abis/abi_1_56/rustc_server.rs
@@ -489,8 +489,8 @@ fn debug_kind(&mut self, _literal: &Self::Literal) -> String {
         // They must still be present to be ABI-compatible and work with upstream proc_macro.
         "".to_owned()
     }
-    fn from_str(&mut self, _s: &str) -> Result<Self::Literal, ()> {
-        unimplemented!()
+    fn from_str(&mut self, s: &str) -> Result<Self::Literal, ()> {
+        Ok(Literal { text: s.into(), id: tt::TokenId::unspecified() })
     }
     fn symbol(&mut self, literal: &Self::Literal) -> String {
         literal.text.to_string()