diff --git a/Makefile b/Makefile
index ef9b5a9a4..f32b0cc7b 100644
--- a/Makefile
+++ b/Makefile
@@ -312,6 +312,14 @@ config.h:
 	echo '#define HAVE_ATTRIBUTE_TARGET 1' >> $@
 	echo '#define HAVE_BUILTIN_CPU_SUPPORT_SSSE3 1' >> $@
 	echo '#endif' >> $@
+	echo '#if defined __linux__' >> $@
+	echo '#define HAVE_GETAUXVAL' >> $@
+	echo '#elif defined __FreeBSD__' >> $@
+	echo '#define HAVE_ELF_AUX_INFO' >> $@
+	echo '#elif defined __OpenBSD__' >> $@
+	echo '// Enable extra OpenBSD checks (see simd.c)' >> $@
+	echo '#define HAVE_OPENBSD' >> $@
+	echo '#endif' >> $@
 
 # And similarly for htslib.pc.tmp ("pkg-config template").  No dependency
 # on htslib.pc.in listed, as if that file is newer the usual way to regenerate
diff --git a/simd.c b/simd.c
index e936e8baa..014a370d6 100644
--- a/simd.c
+++ b/simd.c
@@ -42,6 +42,18 @@ DEALINGS IN THE SOFTWARE.  */
 
 #if defined __arm__ || defined __aarch64__
 
+#ifdef HAVE_OPENBSD
+/*
+ * Extra check for elf_aux_info() on configure-less OpenBSD builds.  Once
+ * version 7.5 has dropped off support, this can be changed to an assumption
+ * that the function exists in the Makefile-generated config.h.
+ */
+#include <sys/param.h>
+#if OpenBSD >= 202409
+#define HAVE_ELF_AUX_INFO
+#endif
+#endif
+
 #if defined HAVE_GETAUXVAL || defined HAVE_ELF_AUX_INFO
 #include <sys/auxv.h>
 #elif defined __APPLE__