diff --git a/crates/mongodb-agent-common/src/interface_types/mongo_agent_error.rs b/crates/mongodb-agent-common/src/interface_types/mongo_agent_error.rs
index d36f8f3e..3f80e2d6 100644
--- a/crates/mongodb-agent-common/src/interface_types/mongo_agent_error.rs
+++ b/crates/mongodb-agent-common/src/interface_types/mongo_agent_error.rs
@@ -15,6 +15,7 @@ pub enum MongoAgentError {
     BadCollectionSchema(String, bson::Bson, bson::de::Error),
     BadQuery(anyhow::Error),
     InvalidVariableName(String),
+    InvalidScalarTypeName(String),
     MongoDB(#[from] mongodb::error::Error),
     MongoDBDeserialization(#[from] mongodb::bson::de::Error),
     MongoDBSerialization(#[from] mongodb::bson::ser::Error),
@@ -64,6 +65,10 @@ impl MongoAgentError {
                 StatusCode::BAD_REQUEST,
                 ErrorResponse::new(&format!("Column identifier includes characters that are not permitted in a MongoDB variable name: {name}"))
             ),
+            InvalidScalarTypeName(name) => (
+                StatusCode::BAD_REQUEST,
+                ErrorResponse::new(&format!("Scalar value includes invalid type name: {name}"))
+            ),
             MongoDB(err) => (StatusCode::BAD_REQUEST, ErrorResponse::new(&err)),
             MongoDBDeserialization(err) => (StatusCode::BAD_REQUEST, ErrorResponse::new(&err)),
             MongoDBSerialization(err) => {
diff --git a/crates/mongodb-agent-common/src/query/make_selector.rs b/crates/mongodb-agent-common/src/query/make_selector.rs
index 974282c0..88317403 100644
--- a/crates/mongodb-agent-common/src/query/make_selector.rs
+++ b/crates/mongodb-agent-common/src/query/make_selector.rs
@@ -21,13 +21,14 @@ fn bson_from_scalar_value(
     value: &serde_json::Value,
     value_type: &str,
 ) -> Result<bson::Bson, MongoAgentError> {
-    // TODO: fail on unrecognized types
     let bson_type = BsonScalarType::from_bson_name(value_type).ok();
     match bson_type {
         Some(t) => {
             json_to_bson_scalar(t, value.clone()).map_err(|e| MongoAgentError::BadQuery(anyhow!(e)))
         }
-        None => bson::to_bson(value).map_err(|e| MongoAgentError::BadQuery(anyhow!(e))),
+        None => Err(MongoAgentError::InvalidScalarTypeName(
+            value_type.to_owned(),
+        )),
     }
 }