diff --git a/src/config.rs b/src/config.rs
index c3837923..30fe6e65 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -59,6 +59,9 @@ pub struct Config {
     pub run_only_ignored: bool,
     /// Filters must match exactly instead of just checking for substrings.
     pub filter_exact: bool,
+    /// Prefix added to all diagnostic code matchers. Note this will make it impossible
+    /// match codes which do not contain this prefix.
+    pub diagnostic_code_prefix: String,
 }
 
 impl Config {
@@ -103,6 +106,7 @@ impl Config {
             list: false,
             run_only_ignored: false,
             filter_exact: false,
+            diagnostic_code_prefix: String::new(),
         }
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 17bec10c..5f6f2a3f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1125,8 +1125,13 @@ fn check_annotations(
                 ErrorMatchKind::Code(code) => {
                     let found = msgs.iter().position(|msg| {
                         msg.level == Level::Error
-                            && msg.code.as_ref().is_some_and(|msg| *msg == **code)
+                            && msg
+                                .code
+                                .as_ref()
+                                .and_then(|code| code.strip_prefix(&config.diagnostic_code_prefix))
+                                .is_some_and(|msg| *msg == **code)
                     });
+
                     if let Some(found) = found {
                         msgs.remove(found);
                         continue;
@@ -1141,7 +1146,10 @@ fn check_annotations(
                 expected_line: Some(line),
             },
             ErrorMatchKind::Code(code) => Error::CodeNotFound {
-                code: code.clone(),
+                code: Spanned::new(
+                    format!("{}{}", config.diagnostic_code_prefix, **code),
+                    code.span(),
+                ),
                 expected_line: Some(line),
             },
         });
diff --git a/src/tests.rs b/src/tests.rs
index 2de55290..0e6c07f9 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -462,3 +462,76 @@ fn main() {
         }
     }
 }
+
+#[test]
+fn find_code_with_prefix() {
+    let s = r"
+fn main() {
+    let _x: i32 = 0u32; //~ E0308
+}
+    ";
+    let comments = Comments::parse(s).unwrap();
+    let config = Config {
+        diagnostic_code_prefix: "prefix::".into(),
+        ..config()
+    };
+    {
+        let messages = vec![
+            vec![],
+            vec![],
+            vec![],
+            vec![Message {
+                message: "mismatched types".to_string(),
+                level: Level::Error,
+                line_col: None,
+                code: Some("prefix::E0308".into()),
+            }],
+        ];
+        let mut errors = vec![];
+        check_annotations(
+            messages,
+            vec![],
+            Path::new("moobar"),
+            &mut errors,
+            &config,
+            "",
+            &comments,
+        )
+        .unwrap();
+        match &errors[..] {
+            [] => {}
+            _ => panic!("{:#?}", errors),
+        }
+    }
+
+    // missing prefix
+    {
+        let messages = vec![
+            vec![],
+            vec![],
+            vec![],
+            vec![Message {
+                message: "mismatched types".to_string(),
+                level: Level::Error,
+                line_col: None,
+                code: Some("E0308".into()),
+            }],
+        ];
+        let mut errors = vec![];
+        check_annotations(
+            messages,
+            vec![],
+            Path::new("moobar"),
+            &mut errors,
+            &config,
+            "",
+            &comments,
+        )
+        .unwrap();
+        match &errors[..] {
+            [Error::CodeNotFound { code, .. }, Error::ErrorsWithoutPattern { msgs, .. }]
+                if **code == "prefix::E0308" && code.line().get() == 3 && msgs.len() == 1 => {}
+            _ => panic!("{:#?}", errors),
+        }
+    }
+}