diff --git a/leptos_macro/Cargo.toml b/leptos_macro/Cargo.toml
index 5b780013c..61be4d48e 100644
--- a/leptos_macro/Cargo.toml
+++ b/leptos_macro/Cargo.toml
@@ -20,7 +20,6 @@ prettyplease = "0.1"
 proc-macro-error = "1"
 proc-macro2 = "1"
 quote = "1"
-serde = "1"
 syn = { version = "1", features = ["full"] }
 syn-rsx = "0.9"
 uuid = { version = "1", features = ["v4"] }
@@ -33,6 +32,7 @@ convert_case = "0.6.0"
 [dev-dependencies]
 log = "0.4"
 typed-builder = "0.11"
+leptos = { path = "../leptos" }
 
 [features]
 default = ["ssr"]
diff --git a/leptos_macro/src/server.rs b/leptos_macro/src/server.rs
index b883d4ddf..821767549 100644
--- a/leptos_macro/src/server.rs
+++ b/leptos_macro/src/server.rs
@@ -43,7 +43,7 @@ pub fn server_macro_impl(args: proc_macro::TokenStream, s: TokenStream2) -> Resu
     let block = body.block;
 
     cfg_if! {
-        if #[cfg(not(feature = "stable"))] {
+        if #[cfg(all(not(feature = "stable"), debug_assertions))] {
             use proc_macro::Span;
             let span = Span::call_site();
             #[cfg(not(target_os = "windows"))]
diff --git a/leptos_server/src/lib.rs b/leptos_server/src/lib.rs
index 575020a26..745910024 100644
--- a/leptos_server/src/lib.rs
+++ b/leptos_server/src/lib.rs
@@ -326,9 +326,19 @@ where
         let mut write = REGISTERED_SERVER_FUNCTIONS
             .write()
             .map_err(|e| ServerFnError::Registration(e.to_string()))?;
-        write.insert(Self::url(), run_server_fn);
+        let prev = write.insert(Self::url(), run_server_fn);
 
-        Ok(())
+        // if there was already a server function with this key,
+        // return Err
+        match prev {
+            Some(_) => Err(ServerFnError::Registration(format!(
+                "There was already a server function registered at {:?}. \
+                This can happen if you use the same server function name in two different modules
+                on `stable` or in `release` mode.",
+                Self::url()
+            ))),
+            None => Ok(()),
+        }
     }
 }