diff --git a/libc/include/bits/fortify/string.h b/libc/include/bits/fortify/string.h
index 4d32b04..041967b 100644
--- a/libc/include/bits/fortify/string.h
+++ b/libc/include/bits/fortify/string.h
@@ -220,8 +220,13 @@
 }
 
 #if __BIONIC_FORTIFY_RUNTIME_CHECKS_ENABLED
-__BIONIC_FORTIFY_INLINE
-size_t strlen(const char* _Nonnull const s __pass_object_size0) __overloadable {
+/*
+ * Clang, when parsing C, can fold strlen to a constant without LLVM's help.
+ * This doesn't apply to overloads of strlen, so write this differently. We
+ * can't use `__pass_object_size0` here, but that's fine: it doesn't help much
+ * on __always_inline functions.
+ */
+extern __always_inline __inline__ __attribute__((gnu_inline)) size_t strlen(const char* _Nonnull s) {
     return __strlen_chk(s, __bos0(s));
 }
 #endif
diff --git a/tests/Android.bp b/tests/Android.bp
index 6aecb40..0bd4a32 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -746,6 +746,40 @@
     },
 }
 
+cc_defaults {
+    name: "bionic_fortify_c_tests_defaults",
+    defaults: [
+        "bionic_clang_fortify_tests_w_flags",
+        "bionic_tests_defaults",
+    ],
+    cflags: [
+        "-U_FORTIFY_SOURCE",
+        // -fbuiltin is required here to counteract -fno-builtin from
+        // `bionic_tests_defaults`. With `-fno-builtin`, Clang won't
+        // const-evaluate calls to `strlen`, which is tested for here.
+        "-fbuiltin",
+    ],
+    srcs: [
+        "clang_fortify_c_only_tests.c",
+    ],
+    tidy: false,
+    shared: {
+        enabled: false,
+    },
+}
+
+cc_test_library {
+    name: "libfortify1-c-tests-clang",
+    defaults: ["bionic_fortify_c_tests_defaults"],
+    cflags: ["-D_FORTIFY_SOURCE=1"],
+}
+
+cc_test_library {
+    name: "libfortify2-c-tests-clang",
+    defaults: ["bionic_fortify_c_tests_defaults"],
+    cflags: ["-D_FORTIFY_SOURCE=2"],
+}
+
 // -----------------------------------------------------------------------------
 // Library of all tests (excluding the dynamic linker tests).
 // -----------------------------------------------------------------------------
@@ -757,8 +791,10 @@
         "libBionicStandardTests",
         "libBionicElfTlsTests",
         "libBionicFramePointerTests",
+        "libfortify1-c-tests-clang",
         "libfortify1-tests-clang",
         "libfortify1-new-tests-clang",
+        "libfortify2-c-tests-clang",
         "libfortify2-tests-clang",
         "libfortify2-new-tests-clang",
     ],
diff --git a/tests/clang_fortify_c_only_tests.c b/tests/clang_fortify_c_only_tests.c
new file mode 100644
index 0000000..3bec848
--- /dev/null
+++ b/tests/clang_fortify_c_only_tests.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <string.h>
+
+// This is a test specifically of bionic's FORTIFY machinery. Other stdlibs need not apply.
+#ifdef __BIONIC__
+
+// Ensure that strlen can be evaluated at compile-time. Clang doesn't support
+// this in C++, but does in C.
+_Static_assert(strlen("foo") == 3, "");
+
+#endif  // __BIONIC__
diff --git a/tests/clang_fortify_tests.cpp b/tests/clang_fortify_tests.cpp
index f08fd1f..105c261 100644
--- a/tests/clang_fortify_tests.cpp
+++ b/tests/clang_fortify_tests.cpp
@@ -89,6 +89,8 @@
 #include <unistd.h>
 #include <wchar.h>
 
+#include <array>
+
 #ifndef COMPILATION_TESTS
 #include <android-base/silent_death_test.h>
 #include <gtest/gtest.h>
@@ -133,6 +135,25 @@
 
 const static int kBogusFD = -1;
 
+FORTIFY_TEST(strlen) {
+  auto run_strlen_with_contents = [&](std::array<char, 3> contents) {
+    // A lot of cruft is necessary to make this test DTRT. LLVM and Clang love to fold/optimize
+    // strlen calls, and that's the opposite of what we want to happen.
+
+    // Loop to convince LLVM that `contents` can never be known (since `xor volatile_value` can flip
+    // any bit in each elem of `contents`).
+    volatile char always_zero = 0;
+    for (char& c : contents) {
+      c ^= always_zero;
+    }
+    // Store in a volatile, so the strlen itself cannot be optimized out.
+    volatile size_t _strlen_result = strlen(&contents.front());
+  };
+
+  EXPECT_NO_DEATH(run_strlen_with_contents({'f', 'o', '\0'}));
+  EXPECT_FORTIFY_DEATH(run_strlen_with_contents({'f', 'o', 'o'}));
+}
+
 FORTIFY_TEST(string) {
   char small_buffer[8] = {};