diff --git a/src/event/attributes.rs b/src/event/attributes.rs
index 120bb9c6..30c1d304 100644
--- a/src/event/attributes.rs
+++ b/src/event/attributes.rs
@@ -1,6 +1,6 @@
 use super::{
     AttributesIntoIteratorV03, AttributesIntoIteratorV10, AttributesV03, AttributesV10,
-    ExtensionValue, SpecVersion,
+    ExtensionValue, SpecVersion, UriReference,
 };
 use chrono::{DateTime, Utc};
 use serde::Serializer;
@@ -14,7 +14,7 @@ pub enum AttributeValue<'a> {
     SpecVersion(SpecVersion),
     String(&'a str),
     URI(&'a Url),
-    URIRef(&'a Url),
+    URIRef(&'a UriReference),
     Boolean(&'a bool),
     Integer(&'a i64),
     Time(&'a DateTime<Utc>),
@@ -49,7 +49,7 @@ pub trait AttributesReader {
     /// Get the [id](https://github.com/cloudevents/spec/blob/master/spec.md#id).
     fn id(&self) -> &str;
     /// Get the [source](https://github.com/cloudevents/spec/blob/master/spec.md#source-1).
-    fn source(&self) -> &Url;
+    fn source(&self) -> &UriReference;
     /// Get the [specversion](https://github.com/cloudevents/spec/blob/master/spec.md#specversion).
     fn specversion(&self) -> SpecVersion;
     /// Get the [type](https://github.com/cloudevents/spec/blob/master/spec.md#type).
@@ -71,7 +71,7 @@ pub trait AttributesWriter {
     fn set_id(&mut self, id: impl Into<String>) -> String;
     /// Set the [source](https://github.com/cloudevents/spec/blob/master/spec.md#source-1).
     /// Returns the previous value.
-    fn set_source(&mut self, source: impl Into<Url>) -> Url;
+    fn set_source(&mut self, source: impl Into<UriReference>) -> UriReference;
     /// Set the [type](https://github.com/cloudevents/spec/blob/master/spec.md#type).
     /// Returns the previous value.
     fn set_type(&mut self, ty: impl Into<String>) -> String;
@@ -126,7 +126,7 @@ impl AttributesReader for Attributes {
         }
     }
 
-    fn source(&self) -> &Url {
+    fn source(&self) -> &UriReference {
         match self {
             Attributes::V03(a) => a.source(),
             Attributes::V10(a) => a.source(),
@@ -184,7 +184,7 @@ impl AttributesWriter for Attributes {
         }
     }
 
-    fn set_source(&mut self, source: impl Into<Url>) -> Url {
+    fn set_source(&mut self, source: impl Into<UriReference>) -> UriReference {
         match self {
             Attributes::V03(a) => a.set_source(source),
             Attributes::V10(a) => a.set_source(source),
diff --git a/src/event/mod.rs b/src/event/mod.rs
index 2d88b7ce..4de44450 100644
--- a/src/event/mod.rs
+++ b/src/event/mod.rs
@@ -20,7 +20,7 @@ pub(crate) use message::EventBinarySerializer;
 pub(crate) use message::EventStructuredSerializer;
 pub use spec_version::SpecVersion;
 pub use spec_version::UnknownSpecVersion;
-pub use types::{TryIntoTime, TryIntoUrl};
+pub use types::{TryIntoTime, TryIntoUrl, UriReference};
 
 mod v03;
 
@@ -85,7 +85,7 @@ pub struct Event {
 #[delegate(self.attributes)]
 impl AttributesReader for Event {
     fn id(&self) -> &str;
-    fn source(&self) -> &Url;
+    fn source(&self) -> &UriReference;
     fn specversion(&self) -> SpecVersion;
     fn ty(&self) -> &str;
     fn datacontenttype(&self) -> Option<&str>;
@@ -97,7 +97,7 @@ impl AttributesReader for Event {
 #[delegate(self.attributes)]
 impl AttributesWriter for Event {
     fn set_id(&mut self, id: impl Into<String>) -> String;
-    fn set_source(&mut self, source: impl Into<Url>) -> Url;
+    fn set_source(&mut self, source: impl Into<UriReference>) -> UriReference;
     fn set_type(&mut self, ty: impl Into<String>) -> String;
     fn set_subject(&mut self, subject: Option<impl Into<String>>) -> Option<String>;
     fn set_time(&mut self, time: Option<impl Into<DateTime<Utc>>>) -> Option<DateTime<Utc>>;
diff --git a/src/event/types.rs b/src/event/types.rs
index 2ae2f649..2a8720f8 100644
--- a/src/event/types.rs
+++ b/src/event/types.rs
@@ -46,3 +46,15 @@ impl TryIntoTime for String {
         self.as_str().into_time()
     }
 }
+
+/// The URI-reference type.
+///
+/// The URI reference can be a URI, or just a relative path.
+///
+/// As the [`url::Url`] type can only represent an absolute URL, we are falling back to a string
+/// here.
+///
+/// Also see:
+/// * https://github.com/cloudevents/spec/blob/v1.0.1/spec.md#type-system
+/// * https://tools.ietf.org/html/rfc3986#section-4.1
+pub type UriReference = String;
diff --git a/src/event/v03/attributes.rs b/src/event/v03/attributes.rs
index cbdb7a23..e26cee71 100644
--- a/src/event/v03/attributes.rs
+++ b/src/event/v03/attributes.rs
@@ -1,6 +1,5 @@
 use crate::event::attributes::{default_hostname, AttributeValue, AttributesConverter};
-use crate::event::AttributesV10;
-use crate::event::{AttributesReader, AttributesWriter, SpecVersion};
+use crate::event::{AttributesReader, AttributesV10, AttributesWriter, SpecVersion, UriReference};
 use crate::message::{BinarySerializer, MessageAttributeValue};
 use chrono::{DateTime, Utc};
 use url::Url;
@@ -22,7 +21,7 @@ pub(crate) const ATTRIBUTE_NAMES: [&str; 8] = [
 pub struct Attributes {
     pub(crate) id: String,
     pub(crate) ty: String,
-    pub(crate) source: Url,
+    pub(crate) source: UriReference,
     pub(crate) datacontenttype: Option<String>,
     pub(crate) schemaurl: Option<Url>,
     pub(crate) subject: Option<String>,
@@ -64,7 +63,7 @@ impl<'a> Iterator for AttributesIntoIterator<'a> {
                 .attributes
                 .schemaurl
                 .as_ref()
-                .map(|v| ("schemaurl", AttributeValue::URIRef(v))),
+                .map(|v| ("schemaurl", AttributeValue::URI(v))),
             6 => self
                 .attributes
                 .subject
@@ -90,7 +89,7 @@ impl AttributesReader for Attributes {
         &self.id
     }
 
-    fn source(&self) -> &Url {
+    fn source(&self) -> &UriReference {
         &self.source
     }
 
@@ -124,7 +123,7 @@ impl AttributesWriter for Attributes {
         std::mem::replace(&mut self.id, id.into())
     }
 
-    fn set_source(&mut self, source: impl Into<Url>) -> Url {
+    fn set_source(&mut self, source: impl Into<UriReference>) -> UriReference {
         std::mem::replace(&mut self.source, source.into())
     }
 
@@ -157,7 +156,7 @@ impl Default for Attributes {
         Attributes {
             id: Uuid::new_v4().to_string(),
             ty: "type".to_string(),
-            source: default_hostname(),
+            source: default_hostname().to_string(),
             datacontenttype: None,
             schemaurl: None,
             subject: None,
@@ -228,7 +227,7 @@ mod tests {
         let a = Attributes {
             id: String::from("1"),
             ty: String::from("someType"),
-            source: Url::parse("https://example.net").unwrap(),
+            source: "https://example.net".into(),
             datacontenttype: None,
             schemaurl: None,
             subject: None,
diff --git a/src/event/v03/builder.rs b/src/event/v03/builder.rs
index d40b4368..3689d95e 100644
--- a/src/event/v03/builder.rs
+++ b/src/event/v03/builder.rs
@@ -1,6 +1,7 @@
 use super::Attributes as AttributesV03;
 use crate::event::{
     Attributes, Data, Event, EventBuilderError, ExtensionValue, TryIntoTime, TryIntoUrl,
+    UriReference,
 };
 use crate::message::MessageAttributeValue;
 use chrono::{DateTime, Utc};
@@ -13,7 +14,7 @@ use url::Url;
 pub struct EventBuilder {
     id: Option<String>,
     ty: Option<String>,
-    source: Option<Url>,
+    source: Option<UriReference>,
     datacontenttype: Option<String>,
     schemaurl: Option<Url>,
     subject: Option<String>,
@@ -29,16 +30,8 @@ impl EventBuilder {
         self
     }
 
-    pub fn source(mut self, source: impl TryIntoUrl) -> Self {
-        match source.into_url() {
-            Ok(u) => self.source = Some(u),
-            Err(e) => {
-                self.error = Some(EventBuilderError::ParseUrlError {
-                    attribute_name: "source",
-                    source: e,
-                })
-            }
-        };
+    pub fn source(mut self, source: impl Into<String>) -> Self {
+        self.source = Some(source.into());
         self
     }
 
@@ -190,7 +183,7 @@ impl crate::event::message::AttributesSerializer for EventBuilder {
         match name {
             "id" => self.id = Some(value.to_string()),
             "type" => self.ty = Some(value.to_string()),
-            "source" => self.source = Some(value.try_into()?),
+            "source" => self.source = Some(value.to_string()),
             "datacontenttype" => self.datacontenttype = Some(value.to_string()),
             "schemaurl" => self.schemaurl = Some(value.try_into()?),
             "subject" => self.subject = Some(value.to_string()),
diff --git a/src/event/v03/format.rs b/src/event/v03/format.rs
index e735e10c..4cb4de65 100644
--- a/src/event/v03/format.rs
+++ b/src/event/v03/format.rs
@@ -18,7 +18,7 @@ impl crate::event::format::EventFormatDeserializer for EventFormatDeserializer {
         Ok(crate::event::Attributes::V03(Attributes {
             id: extract_field!(map, "id", String, E)?,
             ty: extract_field!(map, "type", String, E)?,
-            source: extract_field!(map, "source", String, E, |s: String| Url::parse(&s))?,
+            source: extract_field!(map, "source", String, E)?,
             datacontenttype: extract_optional_field!(map, "datacontenttype", String, E)?,
             schemaurl: extract_optional_field!(map, "schemaurl", String, E, |s: String| {
                 Url::parse(&s)
diff --git a/src/event/v10/attributes.rs b/src/event/v10/attributes.rs
index 4e604424..b52ae152 100644
--- a/src/event/v10/attributes.rs
+++ b/src/event/v10/attributes.rs
@@ -1,5 +1,5 @@
 use crate::event::attributes::{default_hostname, AttributeValue, AttributesConverter};
-use crate::event::{AttributesReader, AttributesV03, AttributesWriter, SpecVersion};
+use crate::event::{AttributesReader, AttributesV03, AttributesWriter, SpecVersion, UriReference};
 use crate::message::{BinarySerializer, MessageAttributeValue};
 use chrono::{DateTime, Utc};
 use core::fmt::Debug;
@@ -22,7 +22,7 @@ pub(crate) const ATTRIBUTE_NAMES: [&str; 8] = [
 pub struct Attributes {
     pub(crate) id: String,
     pub(crate) ty: String,
-    pub(crate) source: Url,
+    pub(crate) source: UriReference,
     pub(crate) datacontenttype: Option<String>,
     pub(crate) dataschema: Option<Url>,
     pub(crate) subject: Option<String>,
@@ -90,7 +90,7 @@ impl AttributesReader for Attributes {
         &self.id
     }
 
-    fn source(&self) -> &Url {
+    fn source(&self) -> &UriReference {
         &self.source
     }
 
@@ -124,7 +124,7 @@ impl AttributesWriter for Attributes {
         std::mem::replace(&mut self.id, id.into())
     }
 
-    fn set_source(&mut self, source: impl Into<Url>) -> Url {
+    fn set_source(&mut self, source: impl Into<UriReference>) -> UriReference {
         std::mem::replace(&mut self.source, source.into())
     }
 
@@ -157,7 +157,7 @@ impl Default for Attributes {
         Attributes {
             id: Uuid::new_v4().to_string(),
             ty: "type".to_string(),
-            source: default_hostname(),
+            source: default_hostname().to_string(),
             datacontenttype: None,
             dataschema: None,
             subject: None,
diff --git a/src/event/v10/builder.rs b/src/event/v10/builder.rs
index 1fceeeeb..e765fe17 100644
--- a/src/event/v10/builder.rs
+++ b/src/event/v10/builder.rs
@@ -1,6 +1,7 @@
 use super::Attributes as AttributesV10;
 use crate::event::{
     Attributes, Data, Event, EventBuilderError, ExtensionValue, TryIntoTime, TryIntoUrl,
+    UriReference,
 };
 use crate::message::MessageAttributeValue;
 use chrono::{DateTime, Utc};
@@ -13,7 +14,7 @@ use url::Url;
 pub struct EventBuilder {
     id: Option<String>,
     ty: Option<String>,
-    source: Option<Url>,
+    source: Option<UriReference>,
     datacontenttype: Option<String>,
     dataschema: Option<Url>,
     subject: Option<String>,
@@ -29,16 +30,8 @@ impl EventBuilder {
         self
     }
 
-    pub fn source(mut self, source: impl TryIntoUrl) -> Self {
-        match source.into_url() {
-            Ok(u) => self.source = Some(u),
-            Err(e) => {
-                self.error = Some(EventBuilderError::ParseUrlError {
-                    attribute_name: "source",
-                    source: e,
-                })
-            }
-        };
+    pub fn source(mut self, source: impl Into<String>) -> Self {
+        self.source = Some(source.into());
         self
     }
 
@@ -190,7 +183,7 @@ impl crate::event::message::AttributesSerializer for EventBuilder {
         match name {
             "id" => self.id = Some(value.to_string()),
             "type" => self.ty = Some(value.to_string()),
-            "source" => self.source = Some(value.try_into()?),
+            "source" => self.source = Some(value.to_string()),
             "datacontenttype" => self.datacontenttype = Some(value.to_string()),
             "dataschema" => self.dataschema = Some(value.try_into()?),
             "subject" => self.subject = Some(value.to_string()),
diff --git a/src/event/v10/format.rs b/src/event/v10/format.rs
index df624639..50f1e361 100644
--- a/src/event/v10/format.rs
+++ b/src/event/v10/format.rs
@@ -18,7 +18,7 @@ impl crate::event::format::EventFormatDeserializer for EventFormatDeserializer {
         Ok(crate::event::Attributes::V10(Attributes {
             id: extract_field!(map, "id", String, E)?,
             ty: extract_field!(map, "type", String, E)?,
-            source: extract_field!(map, "source", String, E, |s: String| Url::parse(&s))?,
+            source: extract_field!(map, "source", String, E)?,
             datacontenttype: extract_optional_field!(map, "datacontenttype", String, E)?,
             dataschema: extract_optional_field!(map, "dataschema", String, E, |s: String| {
                 Url::parse(&s)
diff --git a/src/message/types.rs b/src/message/types.rs
index 7abf2632..721490fc 100644
--- a/src/message/types.rs
+++ b/src/message/types.rs
@@ -1,4 +1,4 @@
-use crate::event::ExtensionValue;
+use crate::event::{ExtensionValue, UriReference};
 use chrono::{DateTime, Utc};
 use std::convert::TryInto;
 use std::fmt;
@@ -12,7 +12,7 @@ pub enum MessageAttributeValue {
     String(String),
     Binary(Vec<u8>),
     Uri(Url),
-    UriRef(Url),
+    UriRef(UriReference),
     DateTime(DateTime<Utc>),
 }
 
@@ -35,7 +35,6 @@ impl TryInto<Url> for MessageAttributeValue {
     fn try_into(self) -> Result<Url, Self::Error> {
         match self {
             MessageAttributeValue::Uri(u) => Ok(u),
-            MessageAttributeValue::UriRef(u) => Ok(u),
             v => Ok(Url::parse(v.to_string().as_ref())?),
         }
     }