diff --git a/libc/include/bits/auxvec.h b/libc/include/bits/auxvec.h
index 4d39477..2d6522a 100644
--- a/libc/include/bits/auxvec.h
+++ b/libc/include/bits/auxvec.h
@@ -37,6 +37,14 @@
 
 #include <linux/auxvec.h>
 
+// AT_HWCAP isn't useful without these constants.
+#if __has_include(<asm/hwcap.h>)
+#include <asm/hwcap.h>
+#endif
+#if __has_include(<asm/hwcap2.h>)
+#include <asm/hwcap2.h>
+#endif
+
 /** Historical SuperH cruft. Irrelevant on Android. */
 #define AT_FPUCW 18
 /** Historical PowerPC cruft. Irrelevant on Android. */
diff --git a/tests/Android.bp b/tests/Android.bp
index 4bd96ad..d1afd51 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -166,6 +166,7 @@
         "strings_nofortify_test.cpp",
         "strings_test.cpp",
         "sstream_test.cpp",
+        "sys_auxv_test.cpp",
         "sys_epoll_test.cpp",
         "sys_mman_test.cpp",
         "sys_msg_test.cpp",
diff --git a/tests/sys_auxv_test.cpp b/tests/sys_auxv_test.cpp
new file mode 100644
index 0000000..afd62ea
--- /dev/null
+++ b/tests/sys_auxv_test.cpp
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2020 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 <gtest/gtest.h>
+
+#include <sys/auxv.h>
+
+TEST(sys_auxv, getauxval_HWCAP) {
+  __attribute__((__unused__)) unsigned long hwcap = getauxval(AT_HWCAP);
+
+  // Check that the constants for *using* AT_HWCAP are also available.
+#if defined(__arm__)
+  ASSERT_NE(0, HWCAP_THUMB);
+#elif defined(__aarch64__)
+  ASSERT_NE(0, HWCAP_FP);
+#endif
+}
+
+TEST(sys_auxv, getauxval_HWCAP2) {
+#if defined(AT_HWCAP2)
+  __attribute__((__unused__)) unsigned long hwcap = getauxval(AT_HWCAP2);
+
+  // Check that the constants for *using* AT_HWCAP2 are also available.
+#if defined(__arm__)
+  ASSERT_NE(0, HWCAP2_AES);
+#elif defined(__aarch64__)
+  ASSERT_NE(0, HWCAP2_SVE2);
+#endif
+#else
+  GTEST_SKIP() << "No AT_HWCAP2 for this architecture.";
+#endif
+}