diff --git a/src/check.rs b/src/check.rs
new file mode 100644
index 0000000000..30fde191bb
--- /dev/null
+++ b/src/check.rs
@@ -0,0 +1,31 @@
+use rustpython_parser::ast::Location;
+use serde::{Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize)]
+pub enum CheckKind {
+    ImportStarUsage,
+    IfTuple,
+}
+
+impl CheckKind {
+    /// A four-letter shorthand code for the check.
+    pub fn code(&self) -> &'static str {
+        match self {
+            CheckKind::ImportStarUsage => "F403",
+            CheckKind::IfTuple => "F634",
+        }
+    }
+
+    /// The body text for the check.
+    pub fn body(&self) -> &'static str {
+        match self {
+            CheckKind::ImportStarUsage => "Unable to detect undefined names",
+            CheckKind::IfTuple => "If test is a tuple, which is always `True`",
+        }
+    }
+}
+
+pub struct Check {
+    pub kind: CheckKind,
+    pub location: Location,
+}
diff --git a/src/checker.rs b/src/checker.rs
index 9f6d04d7f2..791f78576a 100644
--- a/src/checker.rs
+++ b/src/checker.rs
@@ -1,6 +1,6 @@
 use rustpython_parser::ast::{ExprKind, Stmt, StmtKind, Suite};
 
-use crate::message::{Check, CheckKind};
+use crate::check::{Check, CheckKind};
 use crate::visitor::{walk_stmt, Visitor};
 
 struct Checker {
diff --git a/src/lib.rs b/src/lib.rs
index 7f514ed7f0..109e063155 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,8 +1,9 @@
 mod cache;
+mod check;
 pub mod checker;
 pub mod fs;
 pub mod linter;
 pub mod logging;
 pub mod message;
-pub mod parser;
-pub mod visitor;
+mod parser;
+mod visitor;
diff --git a/src/message.rs b/src/message.rs
index af7f16d325..b72400a6eb 100644
--- a/src/message.rs
+++ b/src/message.rs
@@ -4,6 +4,8 @@ use colored::Colorize;
 use rustpython_parser::ast::Location;
 use serde::{Deserialize, Serialize};
 
+use crate::check::CheckKind;
+
 #[derive(Serialize, Deserialize)]
 #[serde(remote = "Location")]
 struct LocationDef {
@@ -19,35 +21,6 @@ impl From<LocationDef> for Location {
     }
 }
 
-#[derive(Serialize, Deserialize)]
-pub enum CheckKind {
-    ImportStarUsage,
-    IfTuple,
-}
-
-impl CheckKind {
-    /// A four-letter shorthand code for the check.
-    pub fn code(&self) -> &'static str {
-        match self {
-            CheckKind::ImportStarUsage => "F403",
-            CheckKind::IfTuple => "F634",
-        }
-    }
-
-    /// The body text for the check.
-    pub fn body(&self) -> &'static str {
-        match self {
-            CheckKind::ImportStarUsage => "Unable to detect undefined names",
-            CheckKind::IfTuple => "If test is a tuple, which is always `True`",
-        }
-    }
-}
-
-pub struct Check {
-    pub kind: CheckKind,
-    pub location: Location,
-}
-
 #[derive(Serialize, Deserialize)]
 pub struct Message {
     pub kind: CheckKind,