diff --git a/parsers/src/cert_management.rs b/parsers/src/cert_management.rs
index 7035b60e14f9642883b4d59dcdead7f1b806cebd..78cc073bb930ae21990ba575b874cb1f6a522dff 100644
--- a/parsers/src/cert_management.rs
+++ b/parsers/src/cert_management.rs
@@ -125,8 +125,8 @@ impl IqSetPayload for Revoke {}
 mod tests {
     use super::*;
     use crate::ns;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
 
     #[cfg(target_pointer_width = "32")]
     #[test]
diff --git a/parsers/src/delay.rs b/parsers/src/delay.rs
index c103fe5f90ddd1c7873951ea2ff5167078cc1234..4d8e31c353425627cd92ac5dc85075ab8450f652 100644
--- a/parsers/src/delay.rs
+++ b/parsers/src/delay.rs
@@ -35,9 +35,9 @@ impl PresencePayload for Delay {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use jid::BareJid;
     use minidom::Element;
-    use std::str::FromStr;
     use xso::error::{Error, FromElementError};
 
     #[cfg(target_pointer_width = "32")]
diff --git a/parsers/src/fast.rs b/parsers/src/fast.rs
index 1f0dd3110467f31efbe226267d53faa4ffd3ba6a..aed0bde75c919822014419d7e7cf4fded25e5f5d 100644
--- a/parsers/src/fast.rs
+++ b/parsers/src/fast.rs
@@ -71,8 +71,8 @@ pub struct Token {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
 
     #[test]
     fn test_simple() {
diff --git a/parsers/src/ibr.rs b/parsers/src/ibr.rs
index 2bd8916bd5ebdcf0da7d05d8f07ee1842e8e14dd..820762769706e009b11572a1e72c42297328e48e 100644
--- a/parsers/src/ibr.rs
+++ b/parsers/src/ibr.rs
@@ -7,8 +7,8 @@
 use crate::data_forms::DataForm;
 use crate::iq::{IqGetPayload, IqResultPayload, IqSetPayload};
 use crate::ns;
+use alloc::collections::BTreeMap;
 use minidom::Element;
-use std::collections::HashMap;
 use xso::error::{Error, FromElementError};
 
 /// Query for registering against a service.
@@ -16,7 +16,7 @@ use xso::error::{Error, FromElementError};
 pub struct Query {
     /// Deprecated fixed list of possible fields to fill before the user can
     /// register.
-    pub fields: HashMap<String, String>,
+    pub fields: BTreeMap<String, String>,
 
     /// Whether this account is already registered.
     pub registered: bool,
@@ -41,7 +41,7 @@ impl TryFrom<Element> for Query {
         check_self!(elem, "query", REGISTER, "IBR query");
         let mut query = Query {
             registered: false,
-            fields: HashMap::new(),
+            fields: BTreeMap::new(),
             remove: false,
             form: None,
         };
@@ -119,13 +119,13 @@ mod tests {
     #[cfg(target_pointer_width = "32")]
     #[test]
     fn test_size() {
-        assert_size!(Query, 88);
+        assert_size!(Query, 68);
     }
 
     #[cfg(target_pointer_width = "64")]
     #[test]
     fn test_size() {
-        assert_size!(Query, 160);
+        assert_size!(Query, 136);
     }
 
     #[test]
diff --git a/parsers/src/idle.rs b/parsers/src/idle.rs
index 54cb235dd7a459ea84b253ca6c46fd53f4ba391f..10d5461bb5d29e5b43b4247908b4bce6a521ccdb 100644
--- a/parsers/src/idle.rs
+++ b/parsers/src/idle.rs
@@ -24,8 +24,8 @@ impl PresencePayload for Idle {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
     use xso::error::{Error, FromElementError};
 
     #[test]
diff --git a/parsers/src/jingle_s5b.rs b/parsers/src/jingle_s5b.rs
index 69eb9b4619b66ff4f4000f287c64835c68071b81..474d6eb8bd96e4cb160efc7632648df080c23dd1 100644
--- a/parsers/src/jingle_s5b.rs
+++ b/parsers/src/jingle_s5b.rs
@@ -309,7 +309,7 @@ impl ::xso::AsXml for Transport {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::str::FromStr;
+    use core::str::FromStr;
 
     #[cfg(target_pointer_width = "32")]
     #[test]
diff --git a/parsers/src/message.rs b/parsers/src/message.rs
index cb377f30b4f6fd38a77e7b9906d97527fff810d9..0c96cbc973854ac9fef1594c0857c8f3dd9786b8 100644
--- a/parsers/src/message.rs
+++ b/parsers/src/message.rs
@@ -402,7 +402,7 @@ impl ::xso::AsXml for Message {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::str::FromStr;
+    use core::str::FromStr;
 
     #[cfg(target_pointer_width = "32")]
     #[test]
diff --git a/parsers/src/muc/muc.rs b/parsers/src/muc/muc.rs
index 613980372c5fd7d5afab123b3659fdb081201b58..68c713f029de16f919f8326386b46ba9af51c106 100644
--- a/parsers/src/muc/muc.rs
+++ b/parsers/src/muc/muc.rs
@@ -100,8 +100,8 @@ impl Muc {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
     use xso::error::{Error, FromElementError};
 
     #[test]
diff --git a/parsers/src/openpgp.rs b/parsers/src/openpgp.rs
index 09c3b633f4374a2c097ea861dabbf8d6e97f59e9..04693dd9fbbc78cfa6dfd499d8f92d38e9844c36 100644
--- a/parsers/src/openpgp.rs
+++ b/parsers/src/openpgp.rs
@@ -67,8 +67,8 @@ mod tests {
         pubsub::{Item as PubSubItem, Publish},
         Item, NodeName,
     };
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
 
     #[test]
     fn pubsub_publish_pubkey_data() {
diff --git a/parsers/src/pubsub/owner.rs b/parsers/src/pubsub/owner.rs
index bc6ec3a6c40303180661c4bb873ae2fb6e766977..b371ec5a3509bc3bb88e121386c25ac8236c626e 100644
--- a/parsers/src/pubsub/owner.rs
+++ b/parsers/src/pubsub/owner.rs
@@ -192,8 +192,8 @@ impl From<PubSubOwner> for Element {
 mod tests {
     use super::*;
     use crate::data_forms::{DataFormType, Field, FieldType};
+    use core::str::FromStr;
     use jid::BareJid;
-    use std::str::FromStr;
 
     #[test]
     fn affiliations() {
diff --git a/parsers/src/roster.rs b/parsers/src/roster.rs
index 6e044bb8d382fa8d9bf001928bd7ee7ca5c57532..e8148578b4a9fc4ce3f7785f10c3c4fb1728bf42 100644
--- a/parsers/src/roster.rs
+++ b/parsers/src/roster.rs
@@ -97,8 +97,8 @@ impl IqResultPayload for Roster {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
     use xso::error::{Error, FromElementError};
 
     #[cfg(target_pointer_width = "32")]
diff --git a/parsers/src/sasl.rs b/parsers/src/sasl.rs
index b18c83438f0c0f14a359448cc552ea51abe631bf..602aff180388c51e98291b31557f16dba8ef336c 100644
--- a/parsers/src/sasl.rs
+++ b/parsers/src/sasl.rs
@@ -7,7 +7,7 @@
 use xso::{text::Base64, AsXml, FromXml};
 
 use crate::ns;
-use std::collections::BTreeMap;
+use alloc::collections::BTreeMap;
 
 generate_attribute!(
     /// The list of available SASL mechanisms.
diff --git a/parsers/src/time.rs b/parsers/src/time.rs
index c01206fc762a7622b46bef862a7e5b7702f84e3d..31c0b1ca99750ccb7fcff107c663005013629330 100644
--- a/parsers/src/time.rs
+++ b/parsers/src/time.rs
@@ -10,8 +10,8 @@ use crate::date::DateTime;
 use crate::iq::{IqGetPayload, IqResultPayload};
 use crate::ns;
 use chrono::FixedOffset;
+use core::str::FromStr;
 use minidom::Element;
-use std::str::FromStr;
 use xso::error::{Error, FromElementError};
 
 /// An entity time query.
diff --git a/parsers/src/tune.rs b/parsers/src/tune.rs
index 84005e33da6c3611ad0dd489c48f97589cea6bf8..d27cf5ebcce643bad0e6b92feadf088345ce7b20 100644
--- a/parsers/src/tune.rs
+++ b/parsers/src/tune.rs
@@ -117,8 +117,8 @@ impl Tune {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
 
     #[cfg(target_pointer_width = "32")]
     #[test]
diff --git a/parsers/src/util/macros.rs b/parsers/src/util/macros.rs
index 569ae74f0f98294cda715eb1a3837cb32ed81961..d5cd47af6aafc89e115bdb212e4a16c1abee5602 100644
--- a/parsers/src/util/macros.rs
+++ b/parsers/src/util/macros.rs
@@ -73,7 +73,7 @@ macro_rules! generate_attribute {
                 $a
             ),+
         }
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<$elem, xso::error::Error> {
                 Ok(match s {
@@ -120,7 +120,7 @@ macro_rules! generate_attribute {
                 $a
             ),+
         }
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<$elem, xso::error::Error> {
                 Ok(match s {
@@ -173,7 +173,7 @@ macro_rules! generate_attribute {
             /// Value when absent.
             None,
         }
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<Self, xso::error::Error> {
                 Ok(match s {
@@ -218,7 +218,7 @@ macro_rules! generate_attribute {
         $(#[$meta])*
         #[derive(Debug, Clone, PartialEq)]
         pub struct $elem(pub $type);
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<Self, xso::error::Error> {
                 Ok($elem($type::from_str(s).map_err(xso::error::Error::text_parse_error)?))
@@ -382,7 +382,7 @@ macro_rules! generate_id {
         $(#[$meta])*
         #[derive(Debug, Clone, PartialEq, Eq, Hash)]
         pub struct $elem(pub String);
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<$elem, xso::error::Error> {
                 // TODO: add a way to parse that differently when needed.
@@ -410,7 +410,7 @@ macro_rules! generate_id {
 macro_rules! generate_elem_id {
     ($(#[$meta:meta])* $elem:ident, $name:literal, $ns:ident) => (
         generate_elem_id!($(#[$meta])* $elem, $name, $ns, String);
-        impl ::std::str::FromStr for $elem {
+        impl ::core::str::FromStr for $elem {
             type Err = xso::error::Error;
             fn from_str(s: &str) -> Result<$elem, xso::error::Error> {
                 // TODO: add a way to parse that differently when needed.
diff --git a/parsers/src/vcard.rs b/parsers/src/vcard.rs
index 93f8af45fcd5e98aef0def04dabf194589c44613..157842c2e885875f6498764aafa22b93e1d29094 100644
--- a/parsers/src/vcard.rs
+++ b/parsers/src/vcard.rs
@@ -73,7 +73,7 @@ impl IqResultPayload for VCard {}
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::str::FromStr;
+    use core::str::FromStr;
 
     #[cfg(target_pointer_width = "32")]
     #[test]
diff --git a/parsers/src/vcard_update.rs b/parsers/src/vcard_update.rs
index 702d41f27c7c2142c3a2aaf9ce708331b44c55bd..b4e58d2d37e9a6dd2cc4966036988bd24abb5ae9 100644
--- a/parsers/src/vcard_update.rs
+++ b/parsers/src/vcard_update.rs
@@ -37,8 +37,8 @@ pub struct Photo {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use core::str::FromStr;
     use minidom::Element;
-    use std::str::FromStr;
 
     #[test]
     fn test_vcard_update() {
diff --git a/parsers/src/xhtml.rs b/parsers/src/xhtml.rs
index 7c99afe9bba3a4fe706a1d6a4274054272059733..28cd30648a0d4240ad684dbf319085a437b9318f 100644
--- a/parsers/src/xhtml.rs
+++ b/parsers/src/xhtml.rs
@@ -6,8 +6,8 @@
 
 use crate::message::MessagePayload;
 use crate::ns;
+use alloc::collections::BTreeMap;
 use minidom::{Element, Node};
-use std::collections::HashMap;
 use xso::error::{Error, FromElementError};
 
 // TODO: Use a proper lang type.
@@ -17,7 +17,7 @@ type Lang = String;
 #[derive(Debug, Clone)]
 pub struct XhtmlIm {
     /// Map of language to body element.
-    bodies: HashMap<Lang, Body>,
+    bodies: BTreeMap<Lang, Body>,
 }
 
 impl XhtmlIm {
@@ -41,7 +41,7 @@ impl XhtmlIm {
 
     /// Removes all unknown elements.
     fn flatten(self) -> XhtmlIm {
-        let mut bodies = HashMap::new();
+        let mut bodies = BTreeMap::new();
         for (lang, body) in self.bodies {
             let children = body.children.into_iter().fold(vec![], |mut acc, child| {
                 match child {
@@ -66,7 +66,7 @@ impl TryFrom<Element> for XhtmlIm {
         check_self!(elem, "html", XHTML_IM);
         check_no_attributes!(elem, "html");
 
-        let mut bodies = HashMap::new();
+        let mut bodies = BTreeMap::new();
         for child in elem.children() {
             if child.is("body", ns::XHTML) {
                 let child = child.clone();
@@ -504,7 +504,7 @@ mod tests {
     #[cfg(target_pointer_width = "32")]
     #[test]
     fn test_size() {
-        assert_size!(XhtmlIm, 32);
+        assert_size!(XhtmlIm, 12);
         assert_size!(Child, 48);
         assert_size!(Tag, 48);
     }
@@ -512,7 +512,7 @@ mod tests {
     #[cfg(target_pointer_width = "64")]
     #[test]
     fn test_size() {
-        assert_size!(XhtmlIm, 48);
+        assert_size!(XhtmlIm, 24);
         assert_size!(Child, 96);
         assert_size!(Tag, 96);
     }