diff --git a/rslib/src/backend/mod.rs b/rslib/src/backend/mod.rs
index 2fe324c77..39aea4675 100644
--- a/rslib/src/backend/mod.rs
+++ b/rslib/src/backend/mod.rs
@@ -33,7 +33,8 @@ use crate::{
     sched::cutoff::local_minutes_west_for_stamp,
     sched::timespan::{answer_button_time, time_span},
     search::{
-        concatenate_searches, negate_search, normalize_search, replace_search_term, SortMode,
+        concatenate_searches, negate_search, normalize_search, replace_search_term, BoolSeparator,
+        SortMode,
     },
     stats::studied_today,
     sync::{
@@ -273,6 +274,17 @@ impl From<pb::DeckConfigId> for DeckConfID {
     }
 }
 
+impl From<i32> for BoolSeparator {
+    fn from(sep: i32) -> Self {
+        use pb::concatenate_searches_in::Separator;
+        match Separator::from_i32(sep) {
+            Some(Separator::And) => BoolSeparator::And,
+            Some(Separator::Or) => BoolSeparator::Or,
+            None => BoolSeparator::And,
+        }
+    }
+}
+
 impl BackendService for Backend {
     fn latest_progress(&self, _input: Empty) -> BackendResult<pb::Progress> {
         let progress = self.progress_state.lock().unwrap().last_progress;
@@ -437,7 +449,7 @@ impl BackendService for Backend {
     }
 
     fn concatenate_searches(&self, input: pb::ConcatenateSearchesIn) -> Result<pb::String> {
-        Ok(concatenate_searches(input.sep, &input.searches)?.into())
+        Ok(concatenate_searches(input.sep.into(), &input.searches)?.into())
     }
 
     fn replace_search_term(&self, input: pb::ReplaceSearchTermIn) -> Result<pb::String> {
diff --git a/rslib/src/search/mod.rs b/rslib/src/search/mod.rs
index aed103b4d..607b9d767 100644
--- a/rslib/src/search/mod.rs
+++ b/rslib/src/search/mod.rs
@@ -5,4 +5,6 @@ mod sqlwriter;
 mod writer;
 
 pub use cards::SortMode;
-pub use writer::{concatenate_searches, negate_search, normalize_search, replace_search_term};
+pub use writer::{
+    concatenate_searches, negate_search, normalize_search, replace_search_term, BoolSeparator,
+};
diff --git a/rslib/src/search/writer.rs b/rslib/src/search/writer.rs
index 2867a64b8..ec7051893 100644
--- a/rslib/src/search/writer.rs
+++ b/rslib/src/search/writer.rs
@@ -2,15 +2,20 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use crate::{
-    backend_proto::concatenate_searches_in::Separator,
     decks::DeckID as DeckIDType,
-    err::{AnkiError, Result},
+    err::Result,
     notetype::NoteTypeID as NoteTypeIDType,
     search::parser::{parse, Node, PropertyKind, SearchNode, StateKind, TemplateKind},
 };
 use itertools::Itertools;
 use std::mem;
 
+#[derive(Debug, PartialEq)]
+pub enum BoolSeparator {
+    And,
+    Or,
+}
+
 /// Take an Anki-style search string and convert it into an equivalent
 /// search string with normalized syntax.
 pub fn normalize_search(input: &str) -> Result<String> {
@@ -38,11 +43,10 @@ pub fn negate_search(input: &str) -> Result<String> {
 /// Take arbitrary Anki-style search strings and return their concatenation where they
 /// are separated by the provided boolean operator.
 /// Empty searches (whole collection) are left out.
-pub fn concatenate_searches(sep: i32, searches: &[String]) -> Result<String> {
-    let bool_node = vec![match Separator::from_i32(sep) {
-        Some(Separator::Or) => Node::Or,
-        Some(Separator::And) => Node::And,
-        None => return Err(AnkiError::SearchError(None)),
+pub fn concatenate_searches(sep: BoolSeparator, searches: &[String]) -> Result<String> {
+    let bool_node = vec![match sep {
+        BoolSeparator::And => Node::And,
+        BoolSeparator::Or => Node::Or,
     }];
     Ok(write_nodes(
         searches
@@ -221,25 +225,22 @@ mod test {
     fn concatenating() -> Result<()> {
         assert_eq!(
             r#""foo" AND "bar""#,
-            concatenate_searches(
-                Separator::And as i32,
-                &["foo".to_string(), "bar".to_string()]
-            )
-            .unwrap()
+            concatenate_searches(BoolSeparator::And, &["foo".to_string(), "bar".to_string()])
+                .unwrap()
         );
         assert_eq!(
             r#""foo" OR "bar""#,
             concatenate_searches(
-                Separator::Or as i32,
+                BoolSeparator::Or,
                 &["foo".to_string(), "".to_string(), "bar".to_string()]
             )
             .unwrap()
         );
         assert_eq!(
             "",
-            concatenate_searches(Separator::Or as i32, &["".to_string()]).unwrap()
+            concatenate_searches(BoolSeparator::Or, &["".to_string()]).unwrap()
         );
-        assert_eq!("", concatenate_searches(Separator::Or as i32, &[]).unwrap());
+        assert_eq!("", concatenate_searches(BoolSeparator::Or, &[]).unwrap());
 
         Ok(())
     }