diff --git a/rslib/src/config/deck.rs b/rslib/src/config/deck.rs
index 89e92e2e3..8c5a7e153 100644
--- a/rslib/src/config/deck.rs
+++ b/rslib/src/config/deck.rs
@@ -19,7 +19,7 @@ impl DeckConfigKey {
 }
 
 impl Collection {
-    pub(crate) fn clear_aux_config_for_deck(&self, ntid: DeckId) -> Result<()> {
+    pub(crate) fn clear_aux_config_for_deck(&mut self, ntid: DeckId) -> Result<()> {
         self.remove_config_prefix(&build_aux_deck_key(ntid, ""))
     }
 
diff --git a/rslib/src/config/mod.rs b/rslib/src/config/mod.rs
index 6a61e18f0..d68ae4414 100644
--- a/rslib/src/config/mod.rs
+++ b/rslib/src/config/mod.rs
@@ -117,9 +117,9 @@ impl Collection {
     }
 
     /// Remove all keys starting with provided prefix, which must end with '_'.
-    pub(crate) fn remove_config_prefix(&self, key: &str) -> Result<()> {
+    pub(crate) fn remove_config_prefix(&mut self, key: &str) -> Result<()> {
         for (key, _val) in self.storage.get_config_prefix(key)? {
-            self.storage.remove_config(&key)?;
+            self.remove_config(key.as_str())?;
         }
         Ok(())
     }
diff --git a/rslib/src/config/notetype.rs b/rslib/src/config/notetype.rs
index 62259e21e..2d289beb4 100644
--- a/rslib/src/config/notetype.rs
+++ b/rslib/src/config/notetype.rs
@@ -33,7 +33,7 @@ impl Collection {
             .map(|_| ())
     }
 
-    pub(crate) fn clear_aux_config_for_notetype(&self, ntid: NotetypeId) -> Result<()> {
+    pub(crate) fn clear_aux_config_for_notetype(&mut self, ntid: NotetypeId) -> Result<()> {
         self.remove_config_prefix(&build_aux_notetype_key(ntid, ""))
     }