diff --git a/src/ErrCtx.zig b/src/ErrCtx.zig
index d28f0f8..83d378d 100644
--- a/src/ErrCtx.zig
+++ b/src/ErrCtx.zig
@@ -12,8 +12,10 @@ const ErrCtx = @This();
 buf: BoundedArray(u8, capacity) =
     BoundedArray(u8, capacity).init(0) catch unreachable,
 overflow: bool = false,
+dirty: bool = false,
 
 pub fn write(self: *ErrCtx, bytes: []const u8) error{}!usize {
+    self.dirty = true;
     const can_add = capacity - self.buf.len;
     if (can_add == 0) return bytes.len;
 
@@ -32,6 +34,10 @@ pub fn writer(self: *ErrCtx) Writer {
     return Writer{ .context = self };
 }
 
+pub fn err(self: *ErrCtx, comptime format: []const u8, args: anytype) void {
+    self.writer().print(format, args) catch unreachable;
+}
+
 pub fn iterator(self: *const ErrCtx) mem.SplitIterator(u8) {
     const slice = self.buf.constSlice();
     const last_byte = if (slice[slice.len - 1] == '0') slice.len - 1 else slice.len;
diff --git a/src/User.zig b/src/User.zig
index 36a59d2..db3e30b 100644
--- a/src/User.zig
+++ b/src/User.zig
@@ -46,34 +46,51 @@ pub fn clone(
 
 // fromLine accepts a line of /etc/passwd (with or without the EOL) and makes a
 // User.
-fn fromLine(allocator: Allocator, err_ctx: anytype, line: []const u8) error{ InvalidRecord, OutOfMemory }!User {
-    _ = err_ctx;
+fn fromLine(allocator: Allocator, err_ctx: *ErrCtx, line: []const u8) error{ InvalidRecord, OutOfMemory }!User {
     var it = mem.split(u8, line, ":");
-    const name = it.next() orelse return error.InvalidRecord;
-    _ = it.next() orelse return error.InvalidRecord; // password
-    const uids = it.next() orelse return error.InvalidRecord;
-    const gids = it.next() orelse return error.InvalidRecord;
-    const gecos = it.next() orelse return error.InvalidRecord;
-    const home = it.next() orelse return error.InvalidRecord;
-    const shell = it.next() orelse return error.InvalidRecord;
+    const name = it.next();
+    _ = it.next(); // password
+    const uids = it.next();
+    const gids = it.next();
+    const gecos = it.next();
+    const home = it.next();
+    const shell = it.next();
+
+    // all fields are set
+    if (shell == null) {
+        err_ctx.err("too few user fields in line: {s}", .{line});
+        return error.InvalidRecord;
+    }
+
     // the line must be exhaustive.
-    if (it.next() != null) return error.InvalidRecord;
+    if (it.next() != null)
+        return error.InvalidRecord;
 
-    const uid = fmt.parseInt(u32, uids, 10) catch return error.InvalidRecord;
-    const gid = fmt.parseInt(u32, gids, 10) catch return error.InvalidRecord;
+    const uid = fmt.parseInt(u32, uids.?, 10) catch {
+        err_ctx.err("bad uid: {s}", .{uids.?});
+        return error.InvalidRecord;
+    };
 
-    try validate.utf8(name);
-    try validate.utf8(gecos);
-    try validate.utf8(home);
-    try validate.utf8(shell);
+    const gid = fmt.parseInt(u32, gids.?, 10) catch {
+        err_ctx.err("bad uid: {s}", .{gids.?});
+        return error.InvalidRecord;
+    };
+
+    validate.utf8(name.?) catch err_ctx.err("name is invalid utf8: {s}", .{name.?});
+    validate.utf8(gecos.?) catch err_ctx.err("gecos is invalid utf8: {s}", .{gecos.?});
+    validate.utf8(home.?) catch err_ctx.err("home is invalid utf8: {s}", .{home.?});
+    validate.utf8(shell.?) catch err_ctx.err("shell is invalid utf8: {s}", .{shell.?});
+
+    if (err_ctx.dirty)
+        return error.InvalidRecord;
 
     const user = User{
         .uid = uid,
         .gid = gid,
-        .name = name,
-        .gecos = gecos,
-        .home = home,
-        .shell = shell,
+        .name = name.?,
+        .gecos = gecos.?,
+        .home = home.?,
+        .shell = shell.?,
     };
     return try user.clone(allocator);
 }
@@ -124,7 +141,7 @@ pub fn deinit(self: *User, allocator: Allocator) void {
     self.* = undefined;
 }
 
-pub fn fromReader(allocator: Allocator, err_ctx: anytype, reader: anytype) ![]User {
+pub fn fromReader(allocator: Allocator, err_ctx: *ErrCtx, reader: anytype) ![]User {
     var users = ArrayList(User).init(allocator);
     errdefer {
         for (users.items) |*user| user.deinit(allocator);
diff --git a/src/unix2db/main.zig b/src/unix2db/main.zig
index 02a0a58..4409e6d 100644
--- a/src/unix2db/main.zig
+++ b/src/unix2db/main.zig
@@ -73,12 +73,16 @@ fn execute(
     defer groupFile.close();
 
     var err_ctx = ErrCtx{};
-
     var users = try User.fromReader(
         allocator,
-        err_ctx.writer(),
+        &err_ctx,
         passwdFile.reader(),
     );
+    errdefer {
+        var it = err_ctx.iterator();
+        while (it.next()) |err|
+            std.debug.print("ERROR: {s}\n", .{err});
+    }
     defer for (users) |*user| user.deinit(allocator);
     defer allocator.free(users);