diff --git a/config.m4.in b/config.m4.in
index ec625731e575115cefda47208ad95672b1ed8b1e..50f9ae7d714d211ad48ed2f14af25547aa05e21c 100644
--- a/config.m4.in
+++ b/config.m4.in
@@ -3,6 +3,7 @@ define(<C_NAME>, <@ASM_SYMBOL_PREFIX@><$1>)dnl
 define(<ELF_STYLE>, <@ASM_ELF_STYLE@>)dnl
 define(<TYPE_FUNCTION>, <@ASM_TYPE_FUNCTION@>)dnl
 define(<ALIGN_LOG>, <@ASM_ALIGN_LOG@>)dnl
+define(<ALIGNOF_UINT64_T>, <@ALIGNOF_UINT64_T@>)dnl
 divert(1)
 @ASM_MARK_NOEXEC_STACK@
 divert
diff --git a/configure.ac b/configure.ac
index 5f2ab76eb2922e026d3ae4c2d3cdee6ff545d7b9..0c1f84bb3770be179b22a338dccb7ad4758c3f45 100644
--- a/configure.ac
+++ b/configure.ac
@@ -479,6 +479,10 @@ AC_TYPE_UID_T
 AC_TYPE_SIZE_T
 AC_HEADER_TIME
 AC_CHECK_SIZEOF(long)
+AC_CHECK_ALIGNOF(uint64_t)
+
+ALIGNOF_UINT64_T="$ac_cv_alignof_uint64_t"
+AC_SUBST(ALIGNOF_UINT64_T)
 
 AC_CHECK_HEADERS([openssl/blowfish.h openssl/des.h openssl/cast.h openssl/aes.h],,
 [enable_openssl=no