diff --git a/src/consensus/encode.rs b/src/consensus/encode.rs
index 9bd8fb45..4f81c42f 100644
--- a/src/consensus/encode.rs
+++ b/src/consensus/encode.rs
@@ -543,8 +543,8 @@ impl Decodable for [u16; 8] {
     #[inline]
     fn consensus_decode<D: io::Read>(mut d: D) -> Result<Self, Error> {
         let mut res = [0; 8];
-        for i in 0..8 {
-            res[i] = Decodable::consensus_decode(&mut d)?;
+        for item in &mut res {
+            *item = Decodable::consensus_decode(&mut d)?;
         }
         Ok(res)
     }
diff --git a/src/network/message_blockdata.rs b/src/network/message_blockdata.rs
index 3326fb52..e2795ef0 100644
--- a/src/network/message_blockdata.rs
+++ b/src/network/message_blockdata.rs
@@ -111,7 +111,7 @@ impl GetBlocksMessage {
     pub fn new(locator_hashes: Vec<BlockHash>, stop_hash: BlockHash) -> GetBlocksMessage {
         GetBlocksMessage {
             version: constants::PROTOCOL_VERSION,
-            locator_hashes: locator_hashes.clone(),
+            locator_hashes: locator_hashes,
             stop_hash: stop_hash
         }
     }
diff --git a/src/util/psbt/macros.rs b/src/util/psbt/macros.rs
index 7844b7ca..80f6678d 100644
--- a/src/util/psbt/macros.rs
+++ b/src/util/psbt/macros.rs
@@ -119,12 +119,12 @@ macro_rules! impl_psbt_insert_pair {
         if !$raw_key.key.is_empty() {
             let key_val: $keyed_key_type = ::util::psbt::serialize::Deserialize::deserialize(&$raw_key.key)?;
 
-            if $slf.$keyed_name.contains_key(&key_val) {
-                return Err(::util::psbt::Error::DuplicateKey($raw_key).into());
-            } else {
-                let val: $keyed_value_type = ::util::psbt::serialize::Deserialize::deserialize(&$raw_value)?;
-
-                $slf.$keyed_name.insert(key_val, val);
+            match $slf.$keyed_name.entry(key_val) {
+                ::std::collections::btree_map::Entry::Vacant(empty_key) => {
+                    let val: $keyed_value_type = ::util::psbt::serialize::Deserialize::deserialize(&$raw_value)?;
+                    empty_key.insert(val);
+                }
+                ::std::collections::btree_map::Entry::Occupied(_) => return Err(::util::psbt::Error::DuplicateKey($raw_key).into()),
             }
         } else {
             return Err(::util::psbt::Error::InvalidKey($raw_key).into());
diff --git a/src/util/psbt/map/global.rs b/src/util/psbt/map/global.rs
index b34b4114..f6b411d4 100644
--- a/src/util/psbt/map/global.rs
+++ b/src/util/psbt/map/global.rs
@@ -13,6 +13,7 @@
 //
 
 use std::collections::BTreeMap;
+use std::collections::btree_map::Entry;
 use std::io::{self, Cursor};
 
 use blockdata::transaction::Transaction;
@@ -60,15 +61,10 @@ impl Map for Global {
         } = pair;
 
         match raw_key.type_value {
-            0u8 => {
-                return Err(Error::DuplicateKey(raw_key).into());
-            }
-            _ => {
-                if self.unknown.contains_key(&raw_key) {
-                    return Err(Error::DuplicateKey(raw_key).into());
-                } else {
-                    self.unknown.insert(raw_key, raw_value);
-                }
+            0u8 => return Err(Error::DuplicateKey(raw_key).into()),
+            _ => match self.unknown.entry(raw_key) {
+                Entry::Vacant(empty_key) => {empty_key.insert(raw_value);},
+                Entry::Occupied(k) => return Err(Error::DuplicateKey(k.key().clone()).into()),
             }
         }
 
@@ -158,12 +154,9 @@ impl Decodable for Global {
                                 return Err(Error::InvalidKey(pair.key).into())
                             }
                         }
-                        _ => {
-                            if unknowns.contains_key(&pair.key) {
-                                return Err(Error::DuplicateKey(pair.key).into());
-                            } else {
-                                unknowns.insert(pair.key, pair.value);
-                            }
+                        _ => match unknowns.entry(pair.key) {
+                            Entry::Vacant(empty_key) => {empty_key.insert(pair.value);},
+                            Entry::Occupied(k) => return Err(Error::DuplicateKey(k.key().clone()).into()),
                         }
                     }
                 }
diff --git a/src/util/psbt/map/input.rs b/src/util/psbt/map/input.rs
index 32f19bc5..05a24432 100644
--- a/src/util/psbt/map/input.rs
+++ b/src/util/psbt/map/input.rs
@@ -112,12 +112,9 @@ impl Map for Input {
                     self.hd_keypaths <= <raw_key: PublicKey>|<raw_value: (Fingerprint, DerivationPath)>
                 }
             }
-            _ => {
-                if self.unknown.contains_key(&raw_key) {
-                    return Err(Error::DuplicateKey(raw_key).into());
-                } else {
-                    self.unknown.insert(raw_key, raw_value);
-                }
+            _ => match self.unknown.entry(raw_key) {
+                ::std::collections::btree_map::Entry::Vacant(empty_key) => {empty_key.insert(raw_value);},
+                ::std::collections::btree_map::Entry::Occupied(k) => return Err(Error::DuplicateKey(k.key().clone()).into()),
             }
         }
 
diff --git a/src/util/psbt/map/output.rs b/src/util/psbt/map/output.rs
index 8219e812..7e32a421 100644
--- a/src/util/psbt/map/output.rs
+++ b/src/util/psbt/map/output.rs
@@ -13,6 +13,7 @@
 //
 
 use std::collections::BTreeMap;
+use std::collections::btree_map::Entry;
 
 use blockdata::script::Script;
 use consensus::encode;
@@ -61,12 +62,9 @@ impl Map for Output {
                     self.hd_keypaths <= <raw_key: PublicKey>|<raw_value: (Fingerprint, DerivationPath)>
                 }
             }
-            _ => {
-                if self.unknown.contains_key(&raw_key) {
-                    return Err(Error::DuplicateKey(raw_key).into());
-                } else {
-                    self.unknown.insert(raw_key, raw_value);
-                }
+            _ => match self.unknown.entry(raw_key) {
+                    Entry::Vacant(empty_key) => {empty_key.insert(raw_value);},
+                    Entry::Occupied(k) => return Err(Error::DuplicateKey(k.key().clone()).into()),
             }
         }