diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5b7e0318..a02c4c48 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1306,12 +1306,6 @@ if(XZ_ARM64_CRC32)
         check_symbol_exists(elf_aux_info sys/auxv.h HAVE_ELF_AUX_INFO)
         tuklib_add_definition_if(liblzma HAVE_ELF_AUX_INFO)
 
-        # OpenBSD has a sysctl() based method. The macro CPU_ID_AA64ISAR0
-        # is used to detect when it's available.
-        check_symbol_exists(CPU_ID_AA64ISAR0 machine/cpu.h
-                            HAVE_CPU_ID_AA64ISAR0)
-        tuklib_add_definition_if(liblzma HAVE_CPU_ID_AA64ISAR0)
-
         # sysctlbyname("hw.optional.armv8_crc32", ...) is supported on Darwin
         # (macOS, iOS, etc.). Note that sysctlbyname() is supported on FreeBSD,
         # NetBSD, and possibly others too but the string is specific to
diff --git a/configure.ac b/configure.ac
index 0ed30eb4..4a277242 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1096,23 +1096,14 @@ int main(void)
 ])
 
 # Check for ARM64 CRC32 instruction runtime detection.
-#
 # getauxval() is supported on Linux, elf_aux_info() on FreeBSD, and
 # sysctlbyname("hw.optional.armv8_crc32", ...) is supported on Darwin
 # (macOS, iOS, etc.). Note that sysctlbyname() is supported on FreeBSD,
 # NetBSD, and possibly others too but the string is specific to Apple OSes.
 # The C code is responsible for checking defined(__APPLE__) before using
 # sysctlbyname("hw.optional.armv8_crc32", ...).
-#
-# sysctl() with CPU_ID_AA64ISAR0 is used on OpenBSD.
 AS_IF([test "x$enable_arm64_crc32" = xyes], [
 	AC_CHECK_FUNCS([getauxval elf_aux_info sysctlbyname], [break])
-	AC_CHECK_DECL([CPU_ID_AA64ISAR0],
-		[AC_DEFINE([HAVE_CPU_ID_AA64ISAR0], [1],
-			[Define to 1 if CPU_ID_AA64ISAR0 is defined
-			in <machine/cpu.h>.])],
-		[],
-		[#include <machine/cpu.h>])
 ])
 
 
diff --git a/src/liblzma/check/crc32_arm64.h b/src/liblzma/check/crc32_arm64.h
index c0609c36..50bac6c7 100644
--- a/src/liblzma/check/crc32_arm64.h
+++ b/src/liblzma/check/crc32_arm64.h
@@ -26,11 +26,6 @@
 #if defined(CRC32_GENERIC) && defined(CRC32_ARCH_OPTIMIZED)
 #	if defined(HAVE_GETAUXVAL) || defined(HAVE_ELF_AUX_INFO)
 #		include <sys/auxv.h>
-#	elif defined(HAVE_CPU_ID_AA64ISAR0)
-#		include <sys/types.h>
-#		include <sys/sysctl.h>
-#		include <machine/cpu.h>
-#		include <machine/armreg.h>
 #	elif defined(_WIN32)
 #		include <processthreadsapi.h>
 #	elif defined(__APPLE__) && defined(HAVE_SYSCTLBYNAME)
@@ -120,16 +115,6 @@ is_arch_extension_supported(void)
 
 	return (feature_flags & HWCAP_CRC32) != 0;
 
-#elif defined(HAVE_CPU_ID_AA64ISAR0)
-	const int isar0_mib[] = { CTL_MACHDEP, CPU_ID_AA64ISAR0 };
-	uint64_t isar0;
-	size_t len = sizeof(isar0);
-
-	if (sysctl(isar0_mib, 2, &isar0, &len, NULL, 0) == -1)
-		return false;
-
-	return ID_AA64ISAR0_CRC32(isar0) >= ID_AA64ISAR0_CRC32_BASE;
-
 #elif defined(_WIN32)
 	return IsProcessorFeaturePresent(
 			PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE);
diff --git a/src/liblzma/check/crc_common.h b/src/liblzma/check/crc_common.h
index afb551a8..abf56927 100644
--- a/src/liblzma/check/crc_common.h
+++ b/src/liblzma/check/crc_common.h
@@ -92,7 +92,6 @@ extern const uint64_t lzma_crc64_table[4][256];
 // Keep this in sync with changes to crc32_arm64.h
 #if defined(_WIN32) || defined(HAVE_GETAUXVAL) \
 		|| defined(HAVE_ELF_AUX_INFO) \
-		|| defined(HAVE_CPU_ID_AA64ISAR0) \
 		|| (defined(__APPLE__) && defined(HAVE_SYSCTLBYNAME))
 #	define CRC_ARM64_RUNTIME_DETECTION 1
 #endif