diff --git a/deltachat-ffi/src/lib.rs b/deltachat-ffi/src/lib.rs
index 04d039a5f..4944dae9b 100644
--- a/deltachat-ffi/src/lib.rs
+++ b/deltachat-ffi/src/lib.rs
@@ -1919,7 +1919,7 @@ pub unsafe extern "C" fn dc_get_contacts(
     let query = to_opt_string_lossy(query);
 
     block_on(async move {
-        match Contact::get_all(ctx, flags, query).await {
+        match Contact::get_all(ctx, flags, query.as_deref()).await {
             Ok(contacts) => Box::into_raw(Box::new(dc_array_t::from(
                 contacts.iter().map(|id| id.to_u32()).collect::<Vec<u32>>(),
             ))),
diff --git a/src/contact.rs b/src/contact.rs
index 0260452df..853caccab 100644
--- a/src/contact.rs
+++ b/src/contact.rs
@@ -686,7 +686,7 @@ impl Contact {
     pub async fn get_all(
         context: &Context,
         listflags: u32,
-        query: Option<impl AsRef<str>>,
+        query: Option<&str>,
     ) -> Result<Vec<ContactId>> {
         let self_addrs = context.get_all_self_addrs().await?;
         let mut add_self = false;
@@ -695,7 +695,7 @@ impl Contact {
         let flag_add_self = (listflags & DC_GCL_ADD_SELF) != 0;
 
         if flag_verified_only || query.is_some() {
-            let s3str_like_cmd = format!("%{}%", query.as_ref().map(|s| s.as_ref()).unwrap_or(""));
+            let s3str_like_cmd = format!("%{}%", query.unwrap_or(""));
             context
                 .sql
                 .query_map(
@@ -739,9 +739,9 @@ impl Contact {
                     .unwrap_or_default();
                 let self_name2 = stock_str::self_msg(context);
 
-                if self_addr.contains(query.as_ref())
-                    || self_name.contains(query.as_ref())
-                    || self_name2.await.contains(query.as_ref())
+                if self_addr.contains(query)
+                    || self_name.contains(query)
+                    || self_name2.await.contains(query)
                 {
                     add_self = true;
                 }
@@ -1396,27 +1396,23 @@ pub fn normalize_name(full_name: &str) -> String {
 fn cat_fingerprint(
     ret: &mut String,
     addr: &str,
-    fingerprint_verified: impl AsRef<str>,
-    fingerprint_unverified: impl AsRef<str>,
+    fingerprint_verified: &str,
+    fingerprint_unverified: &str,
 ) {
     *ret += &format!(
         "\n\n{}:\n{}",
         addr,
-        if !fingerprint_verified.as_ref().is_empty() {
-            fingerprint_verified.as_ref()
+        if !fingerprint_verified.is_empty() {
+            fingerprint_verified
         } else {
-            fingerprint_unverified.as_ref()
+            fingerprint_unverified
         },
     );
-    if !fingerprint_verified.as_ref().is_empty()
-        && !fingerprint_unverified.as_ref().is_empty()
-        && fingerprint_verified.as_ref() != fingerprint_unverified.as_ref()
+    if !fingerprint_verified.is_empty()
+        && !fingerprint_unverified.is_empty()
+        && fingerprint_verified != fingerprint_unverified
     {
-        *ret += &format!(
-            "\n\n{} (alternative):\n{}",
-            addr,
-            fingerprint_unverified.as_ref()
-        );
+        *ret += &format!("\n\n{} (alternative):\n{}", addr, fingerprint_unverified);
     }
 }
 
diff --git a/src/dc_receive_imf.rs b/src/dc_receive_imf.rs
index ee95c529f..f03f6bb24 100644
--- a/src/dc_receive_imf.rs
+++ b/src/dc_receive_imf.rs
@@ -2920,7 +2920,7 @@ mod tests {
 
         let chats = Chatlist::try_load(&t.ctx, 0, None, None).await?;
         assert_eq!(chats.len(), 1);
-        let contacts = Contact::get_all(&t.ctx, 0, None as Option<String>).await?;
+        let contacts = Contact::get_all(&t.ctx, 0, None).await?;
         assert_eq!(contacts.len(), 0); // mailing list recipients and senders do not count as "known contacts"
 
         let msg1 = get_chat_msg(&t, chat_id, 0, 2).await;
diff --git a/src/login_param.rs b/src/login_param.rs
index 85c2e0e66..a83f83f78 100644
--- a/src/login_param.rs
+++ b/src/login_param.rs
@@ -150,8 +150,7 @@ impl LoginParam {
     }
 
     /// Read the login parameters from the database.
-    async fn from_database(context: &Context, prefix: impl AsRef<str>) -> Result<Self> {
-        let prefix = prefix.as_ref();
+    async fn from_database(context: &Context, prefix: &str) -> Result<Self> {
         let sql = &context.sql;
 
         let key = format!("{}addr", prefix);