diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69fc35eace17a56e0bbf99eff1626fbb96ce9cf0..ff2f16993cefa6a4e096634687b07948833207b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 - feat: clarify "defined runtime representation" and "can be represented at runtime"
 - fix(sema): fix passing structs as function params
+- fix: diagnostic box drawing characters line up after line 9
+- fix: diagnostics on last line of file print correctly
 
 ## 0.1.4
 
diff --git a/src/core/Report.zig b/src/core/Report.zig
index c58c32f0234448ed1f24c073a6de01e0c17bd1a8..86c8df1f8bf7d39d1f66ff2819448a91ebb0a289 100644
--- a/src/core/Report.zig
+++ b/src/core/Report.zig
@@ -610,8 +610,8 @@ const Prefix = enum {
 
     fn symbol(prefix: Prefix, ascii: bool) []const u8 {
         return switch (prefix) {
-            .@"error" => if (ascii) " X " else " ✘ ",
-            .warn => if (ascii) " ! " else " ▲ ",
+            .@"error" => if (ascii) "X" else "✘",
+            .warn => if (ascii) "!" else "▲",
             .note => "",
         };
     }
@@ -676,6 +676,17 @@ pub fn formatItem(
 
     assert(ctx.components.items.len > 0);
 
+    const width = brk: {
+        var max: usize = 0;
+        for (ctx.components.items) |component| {
+            if (component.location) |loc| {
+                max = @max(loc.loc.line.oneBased(), max);
+            }
+        }
+
+        break :brk if (max > 0) std.fmt.count("{d}", .{max}) else 0;
+    };
+
     for (ctx.components.items, 1..) |component, i| {
         const prefix: Prefix = if (i == 1)
             switch (item_type) {
@@ -686,15 +697,18 @@ pub fn formatItem(
 
         const is_last = i == ctx.components.items.len;
 
+        try writer.writeByteNTimes(' ', width);
+
         if (i != 1) {
             try tty.setColor(writer, .dim);
-            try writer.writeAll(" │ ");
+            try writer.writeAll("│");
             try tty.setColor(writer, .reset);
         }
 
         try tty.setColor(writer, prefix.color());
         try tty.setColor(writer, .bold);
         try writer.writeAll(prefix.symbol(false));
+        try writer.writeAll(" ");
         try writer.writeAll(@tagName(prefix));
         try tty.setColor(writer, .reset);
         try tty.setColor(writer, .dim);
@@ -712,7 +726,8 @@ pub fn formatItem(
         const at = component.location orelse {
             if (is_last) {
                 try tty.setColor(writer, .dim);
-                try writer.print(" {s}", .{"┴"});
+                try writer.writeByteNTimes(' ', width);
+                try writer.print("{s}", .{"┴"});
                 try writer.writeAll("\n");
                 try tty.setColor(writer, .reset);
             }
@@ -721,8 +736,13 @@ pub fn formatItem(
 
         const line_before = utf8_source[at.loc.line_start..at.byte];
         const trimmed_before = std.mem.trimLeft(u8, line_before, " \t\r");
-        const line_after = utf8_source[at.byte + at.slice.len .. at.loc.line_end + 1];
-        const width = std.fmt.count("{d}", .{at.loc.line.oneBased()});
+        // The text after the highlighted component can be out of bounds if the
+        // highlighted token is EOF, which is hardcoded to "   " to highlight
+        // empty space after the line.
+        const line_after = if (at.byte + at.slice.len < at.loc.line_end)
+            utf8_source[at.byte + at.slice.len .. at.loc.line_end]
+        else
+            "";
 
         try tty.setColor(writer, .dim);
         try writer.writeByteNTimes(' ', width);
@@ -741,12 +761,13 @@ pub fn formatItem(
         try writer.writeAll(at.slice);
         try tty.setColor(writer, .reset);
         try writer.writeAll(line_after);
+        try writer.writeAll("\n");
         try tty.setColor(writer, .dim);
-        try writer.writeAll(if (is_last) " ╰" else " ├");
+        try writer.writeByteNTimes(' ', width);
+        try writer.writeAll(if (is_last) "╰" else "├");
         try writer.writeBytesNTimes(
             "─",
-            width +
-                (at.byte - at.loc.line_start) -
+            1 + (at.byte - at.loc.line_start) -
                 (line_before.len - trimmed_before.len),
         );
         try tty.setColor(writer, .reset);
@@ -912,7 +933,10 @@ pub const Highlight = union(enum) {
 
                 break :loc .{
                     .loc = location,
-                    .slice = if (token.tag != .eof) token.slice(ast.utf8_source) else "\n",
+                    .slice = if (token.tag != .eof)
+                        token.slice(ast.utf8_source)
+                    else
+                        "   ",
                     .byte = token.offset,
                 };
             },