diff --git a/rslib/build.rs b/rslib/build.rs
index 8a7d2362b..061c88ca2 100644
--- a/rslib/build.rs
+++ b/rslib/build.rs
@@ -3,10 +3,9 @@
 
 mod rust_interface;
 
-use std::env;
 use std::fs;
-use std::path::PathBuf;
 
+use anki_proto_gen::descriptors_path;
 use anyhow::Result;
 use prost_reflect::DescriptorPool;
 
@@ -15,7 +14,7 @@ fn main() -> Result<()> {
     let buildhash = fs::read_to_string("../out/buildhash").unwrap_or_default();
     println!("cargo:rustc-env=BUILDHASH={buildhash}");
 
-    let descriptors_path = env::var("DESCRIPTORS_BIN").ok().map(PathBuf::from).unwrap();
+    let descriptors_path = descriptors_path();
     println!("cargo:rerun-if-changed={}", descriptors_path.display());
     let pool = DescriptorPool::decode(std::fs::read(descriptors_path)?.as_ref())?;
     rust_interface::write_rust_interface(&pool)?;
diff --git a/rslib/proto/build.rs b/rslib/proto/build.rs
index 5e5e1359a..e75f3367b 100644
--- a/rslib/proto/build.rs
+++ b/rslib/proto/build.rs
@@ -5,14 +5,12 @@ pub mod python;
 pub mod rust;
 pub mod ts;
 
-use std::env;
-use std::path::PathBuf;
-
+use anki_proto_gen::descriptors_path;
 use anki_proto_gen::get_services;
 use anyhow::Result;
 
 fn main() -> Result<()> {
-    let descriptors_path = env::var("DESCRIPTORS_BIN").ok().map(PathBuf::from);
+    let descriptors_path = descriptors_path();
 
     let pool = rust::write_rust_protos(descriptors_path)?;
     let (_, services) = get_services(&pool);
diff --git a/rslib/proto/rust.rs b/rslib/proto/rust.rs
index 8a559ba8d..c3af4fe77 100644
--- a/rslib/proto/rust.rs
+++ b/rslib/proto/rust.rs
@@ -14,7 +14,7 @@ use anyhow::Context;
 use anyhow::Result;
 use prost_reflect::DescriptorPool;
 
-pub fn write_rust_protos(descriptors_path: Option<PathBuf>) -> Result<DescriptorPool> {
+pub fn write_rust_protos(descriptors_path: PathBuf) -> Result<DescriptorPool> {
     set_protoc_path();
     let proto_dir = PathBuf::from("../../proto");
     let paths = gather_proto_paths(&proto_dir)?;
@@ -49,14 +49,12 @@ pub fn write_rust_protos(descriptors_path: Option<PathBuf>) -> Result<Descriptor
         .context("prost build")?;
 
     let descriptors = read_file(&tmp_descriptors)?;
-    if let Some(descriptors_path) = descriptors_path {
-        create_dir_all(
-            descriptors_path
-                .parent()
-                .context("missing parent of descriptor")?,
-        )?;
-        write_file_if_changed(descriptors_path, &descriptors)?;
-    }
+    create_dir_all(
+        descriptors_path
+            .parent()
+            .context("missing parent of descriptor")?,
+    )?;
+    write_file_if_changed(descriptors_path, &descriptors)?;
 
     let pool = DescriptorPool::decode(descriptors.as_ref())?;
     add_must_use_annotations(
diff --git a/rslib/proto_gen/src/lib.rs b/rslib/proto_gen/src/lib.rs
index d5dd88e07..6b424bcac 100644
--- a/rslib/proto_gen/src/lib.rs
+++ b/rslib/proto_gen/src/lib.rs
@@ -5,6 +5,7 @@
 //! match.
 
 use std::collections::HashMap;
+use std::env;
 use std::path::PathBuf;
 
 use anki_io::read_to_string;
@@ -266,3 +267,14 @@ pub fn determine_if_message_is_empty(pool: &DescriptorPool, path: &Utf8Path, nam
         false
     }
 }
+
+/// - When building via a local checkout, the path defined in .cargo/config
+/// - When building via cargo install or a third-party crate,
+///   OUT_DIR/../../anki_descriptors.bin (so it can be seen by the rslib crate)
+pub fn descriptors_path() -> PathBuf {
+    if let Ok(path) = env::var("DESCRIPTORS_BIN") {
+        PathBuf::from(path)
+    } else {
+        PathBuf::from(env::var("OUT_DIR").unwrap()).join("../../anki_descriptors.bin")
+    }
+}