diff --git a/src/Compilation.zig b/src/Compilation.zig
index f202034242fd917a00988094b3b941945ea250b7..fececba06651bf61b2add950d59f2c20a8e0bc49 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -403,10 +403,10 @@ pub const AllErrors = struct {
             const source = try module_note.src_loc.file_scope.getSource(module.gpa);
             const byte_offset = try module_note.src_loc.byteOffset(module.gpa);
             const loc = std.zig.findLineColumn(source, byte_offset);
-            const sub_file_path = module_note.src_loc.file_scope.sub_file_path;
+            const file_path = try module_note.src_loc.file_scope.fullPath(&arena.allocator);
             note.* = .{
                 .src = .{
-                    .src_path = try arena.allocator.dupe(u8, sub_file_path),
+                    .src_path = file_path,
                     .msg = try arena.allocator.dupe(u8, module_note.msg),
                     .byte_offset = byte_offset,
                     .line = @intCast(u32, loc.line),
@@ -426,10 +426,10 @@ pub const AllErrors = struct {
         const source = try module_err_msg.src_loc.file_scope.getSource(module.gpa);
         const byte_offset = try module_err_msg.src_loc.byteOffset(module.gpa);
         const loc = std.zig.findLineColumn(source, byte_offset);
-        const sub_file_path = module_err_msg.src_loc.file_scope.sub_file_path;
+        const file_path = try module_err_msg.src_loc.file_scope.fullPath(&arena.allocator);
         try errors.append(.{
             .src = .{
-                .src_path = try arena.allocator.dupe(u8, sub_file_path),
+                .src_path = file_path,
                 .msg = try arena.allocator.dupe(u8, module_err_msg.msg),
                 .byte_offset = byte_offset,
                 .line = @intCast(u32, loc.line),
@@ -480,7 +480,7 @@ pub const AllErrors = struct {
 
                     note.* = .{
                         .src = .{
-                            .src_path = try arena.dupe(u8, file.sub_file_path),
+                            .src_path = try file.fullPath(arena),
                             .msg = try arena.dupe(u8, msg),
                             .byte_offset = byte_offset,
                             .line = @intCast(u32, loc.line),
@@ -506,7 +506,7 @@ pub const AllErrors = struct {
 
             try errors.append(.{
                 .src = .{
-                    .src_path = try arena.dupe(u8, file.sub_file_path),
+                    .src_path = try file.fullPath(arena),
                     .msg = try arena.dupe(u8, msg),
                     .byte_offset = byte_offset,
                     .line = @intCast(u32, loc.line),
diff --git a/src/Module.zig b/src/Module.zig
index 439256f32063b14594751c2963af6f3c2c3ab5cc..e192b0100447c4b046096956ea3c73d4fd27e468 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -1111,6 +1111,10 @@ pub const Scope = struct {
             return buf.toOwnedSliceSentinel(0);
         }
 
+        pub fn fullPath(file: File, ally: *Allocator) ![]u8 {
+            return file.pkg.root_src_directory.join(ally, &[_][]const u8{file.sub_file_path});
+        }
+
         pub fn dumpSrc(file: *File, src: LazySrcLoc) void {
             const loc = std.zig.findLineColumn(file.source.bytes, src);
             std.debug.print("{s}:{d}:{d}\n", .{ file.sub_file_path, loc.line + 1, loc.column + 1 });