diff --git a/tests/Lint/main.cpp b/tests/Lint/main.cpp
index 69bd436..4e07d94 100644
--- a/tests/Lint/main.cpp
+++ b/tests/Lint/main.cpp
@@ -6,6 +6,9 @@ import Crafter.Build;
 namespace fs = std::filesystem;
 using namespace Crafter;
 
+extern "C" int setenv(const char* name, const char* value, int overwrite);
+extern "C" int unsetenv(const char* name);
+
 namespace {
     std::int32_t Failures = 0;
 
@@ -705,6 +708,31 @@ int main() {
         // two assertions above cover it.
     }
 
+    // A configuration whose std module cannot be built is in the build graph
+    // all the same: its files cannot be parsed, which has to fail the run.
+    // Its command was cleared, which read as "not a translation unit", and
+    // every semantic rule passed the files. A sysroot without libc++ is one
+    // way there. The std module's directory is made before its build fails,
+    // so the cache is redirected around this run.
+    {
+        Scratch s("ast-no-std-module");
+        s.Write("f", "int Value = 1;\n");
+        Configuration cfg = s.Config({"f"});
+        cfg.sysroot = (s.dir / "empty-sysroot").string();
+        fs::create_directories(cfg.sysroot);
+        bool ran = false;
+        cfg.AddAstLintRule("needs-ast", [&ran](LintContext&) { ran = true; });
+        const char* realCache = std::getenv("XDG_CACHE_HOME");
+        const std::string saved = realCache ? realCache : "";
+        setenv("XDG_CACHE_HOME", (s.dir / "cache").c_str(), 1);
+        LintSummary summary = RunLint(cfg, Mode(LintMode::Report));
+        if (saved.empty()) unsetenv("XDG_CACHE_HOME");
+        else setenv("XDG_CACHE_HOME", saved.c_str(), 1);
+        Check(!ran, "ast: rule is skipped when the std module cannot be built");
+        Check(summary.errors > 0, "ast: a std module that cannot be built fails the run");
+        Check(!summary.Clean(), "ast: a std module that cannot be built is not Clean");
+    }
+
     // --no-ast skips those rules deliberately and exits normally.
     {
         Scratch s("ast-optout");