diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e3063a0..e8323e51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Breaking changes
+
+- Add custom variant to `AttachmentType` that holds an arbitrary String. ([#916](https://github.com/getsentry/sentry-rust/pull/916))
+
 ## 0.44.0
 
 ### Breaking changes
diff --git a/sentry-types/src/protocol/attachment.rs b/sentry-types/src/protocol/attachment.rs
index 8b2ce6d7..e23a6478 100644
--- a/sentry-types/src/protocol/attachment.rs
+++ b/sentry-types/src/protocol/attachment.rs
@@ -3,7 +3,7 @@ use std::fmt;
 use serde::Deserialize;
 
 /// The different types an attachment can have.
-#[derive(Debug, Copy, Clone, Eq, PartialEq, Deserialize)]
+#[derive(Debug, Clone, Eq, PartialEq, Deserialize)]
 pub enum AttachmentType {
     #[serde(rename = "event.attachment")]
     /// (default) A standard attachment without special meaning.
@@ -23,6 +23,9 @@ pub enum AttachmentType {
     /// the last logs are extracted into event breadcrumbs.
     #[serde(rename = "unreal.logs")]
     UnrealLogs,
+    /// A custom attachment type with an arbitrary string value.
+    #[serde(untagged)]
+    Custom(String),
 }
 
 impl Default for AttachmentType {
@@ -33,13 +36,14 @@ impl Default for AttachmentType {
 
 impl AttachmentType {
     /// Gets the string value Sentry expects for the attachment type.
-    pub fn as_str(self) -> &'static str {
+    pub fn as_str(&self) -> &str {
         match self {
             Self::Attachment => "event.attachment",
             Self::Minidump => "event.minidump",
             Self::AppleCrashReport => "event.applecrashreport",
             Self::UnrealContext => "unreal.context",
             Self::UnrealLogs => "unreal.logs",
+            Self::Custom(s) => s,
         }
     }
 }
@@ -68,7 +72,11 @@ impl Attachment {
             r#"{{"type":"attachment","length":{length},"filename":"{filename}","attachment_type":"{at}","content_type":"{ct}"}}"#,
             filename = self.filename,
             length = self.buffer.len(),
-            at = self.ty.unwrap_or_default().as_str(),
+            at = self
+                .ty
+                .as_ref()
+                .unwrap_or(&AttachmentType::default())
+                .as_str(),
             ct = self
                 .content_type
                 .as_ref()
@@ -92,3 +100,18 @@ impl fmt::Debug for Attachment {
             .finish()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json;
+
+    #[test]
+    fn test_attachment_type_deserialize() {
+        let result: AttachmentType = serde_json::from_str(r#""event.minidump""#).unwrap();
+        assert_eq!(result, AttachmentType::Minidump);
+
+        let result: AttachmentType = serde_json::from_str(r#""my.custom.type""#).unwrap();
+        assert_eq!(result, AttachmentType::Custom("my.custom.type".to_string()));
+    }
+}