diff --git a/gdn/src/data.rs b/gdn/src/data.rs
index 29fcd14..a405bee 100644
--- a/gdn/src/data.rs
+++ b/gdn/src/data.rs
@@ -15,10 +15,12 @@ pub use self::{
 
 fn migrate(dir: &LockedDataDir) -> anyhow::Result<()> {
     loop {
-        match dir.read_version()? {
-            0 => v0::migrate(dir)?,
+        let version = dir.read_version().context("failed to migrate data dir")?;
+        match version {
+            0 => v0::migrate(dir),
             _ => break Ok(()),
         }
+        .with_context(|| format!("failed to migrate data dir from version {version}"))?;
     }
 }
 
diff --git a/gdn/src/data/datadir.rs b/gdn/src/data/datadir.rs
index 6b23866..c4ee5bf 100644
--- a/gdn/src/data/datadir.rs
+++ b/gdn/src/data/datadir.rs
@@ -104,6 +104,7 @@ impl UnlockedDataDir {
     pub(super) fn read_version(&self) -> anyhow::Result<u32> {
         let path = self.version_file();
         match self.read_string_optional(&path)? {
+            None if self.path.exists() => Err(anyhow!("found data dir without version number")),
             None => Ok(0),
             Some(string) => Ok(string.trim().parse().with_context(|| {
                 format!("failed to parse {} as version number", path.display())