diff --git a/lib/compiler/Maker/Step.zig b/lib/compiler/Maker/Step.zig
index 5c618660ce787ce8913b9dfb597f0bf882856b7e..5854bbbf25305e46eb3483e89948caa843f9f408 100644
--- a/lib/compiler/Maker/Step.zig
+++ b/lib/compiler/Maker/Step.zig
@@ -18,6 +18,7 @@ const assert = std.debug.assert;
 const WebServer = @import("WebServer.zig");
 const Maker = @import("../Maker.zig");
 
+pub const CheckFile = @import("Step/CheckFile.zig");
 pub const Compile = @import("Step/Compile.zig");
 pub const FindProgram = @import("Step/FindProgram.zig");
 pub const Fmt = @import("Step/Fmt.zig");
@@ -75,7 +76,7 @@ comptime {
 }
 
 pub const Extended = union(enum) {
-    check_file: Todo,
+    check_file: CheckFile,
     compile: Compile,
     config_header: Todo,
     fail: Fail,
diff --git a/lib/compiler/Maker/Step/CheckFile.zig b/lib/compiler/Maker/Step/CheckFile.zig
index 0ed23c05e01952091d0c02ff26a642446e9ae1a0..ab563a6092ee759f1e636eab9cee1b3b6759d203 100644
--- a/lib/compiler/Maker/Step/CheckFile.zig
+++ b/lib/compiler/Maker/Step/CheckFile.zig
@@ -13,6 +13,7 @@ pub fn make(
     maker: *Maker,
     progress_node: std.Progress.Node,
 ) Step.ExtendedMakeError!void {
+    _ = check_file;
     _ = progress_node;
     const graph = maker.graph;
     const arena = maker.graph.arena; // TODO don't leak into process arena
@@ -20,7 +21,7 @@ pub fn make(
     const step = maker.stepByIndex(step_index);
     const conf = &maker.scanned_config.configuration;
     const conf_step = step_index.ptr(conf);
-    const conf_cf = conf_step.extended.get(conf.extra).install_file;
+    const conf_cf = conf_step.extended.get(conf.extra).check_file;
     const lazy_path = conf_cf.file.get(conf);
 
     try step.singleUnchangingWatchInput(maker, arena, lazy_path);
@@ -29,11 +30,12 @@ pub fn make(
     const limit: Io.Limit = if (conf_cf.max_bytes.value) |x| .limited(x) else .unlimited;
 
     const contents = src_path.root_dir.handle.readFileAlloc(io, src_path.sub_path, arena, limit) catch |err|
-        return step.fail("failed to read {f}: {t}", .{ src_path, err });
+        return step.fail(maker, "failed to read {f}: {t}", .{ src_path, err });
 
-    for (check_file.expected_matches) |expected_match| {
+    for (conf_cf.expected_matches.slice) |expected_match_index| {
+        const expected_match = expected_match_index.slice(conf);
         if (std.mem.find(u8, contents, expected_match) == null) {
-            return step.fail(
+            return step.fail(maker,
                 \\
                 \\========= expected to find: ===================
                 \\{s}
@@ -44,16 +46,17 @@ pub fn make(
         }
     }
 
-    if (check_file.expected_exact) |expected_exact| {
+    if (conf_cf.expected_exact.value) |expected_exact_index| {
+        const expected_exact = expected_exact_index.slice(conf);
         if (!std.mem.eql(u8, expected_exact, contents)) {
-            return step.fail(
+            return step.fail(maker,
                 \\
                 \\========= expected: =====================
                 \\{s}
                 \\========= but found: ====================
                 \\{s}
                 \\========= from the following file: ======
-                \\{s}
+                \\{f}
             , .{ expected_exact, contents, src_path });
         }
     }