diff --git a/include/simdjson/arm64.h b/include/simdjson/arm64.h
index 6cbc0bffc..b8c33401a 100644
--- a/include/simdjson/arm64.h
+++ b/include/simdjson/arm64.h
@@ -6,7 +6,11 @@
 #endif
 
 #include "simdjson/portability.h"
-
+// Default Haswell to on if this is x86-64. Even if we're not compiled for it, it could be selected
+// at runtime.
+#ifndef SIMDJSON_IMPLEMENTATION_ARM64
+#define SIMDJSON_IMPLEMENTATION_ARM64 (SIMDJSON_IS_ARM64)
+#endif
 #include "simdjson/internal/isadetection.h"
 #include "simdjson/internal/jsoncharutils_tables.h"
 #include "simdjson/internal/numberparsing_tables.h"
diff --git a/include/simdjson/ppc64.h b/include/simdjson/ppc64.h
index a03cc347f..47e5d4f83 100644
--- a/include/simdjson/ppc64.h
+++ b/include/simdjson/ppc64.h
@@ -7,6 +7,10 @@
 
 #include "simdjson/portability.h"
 
+#ifndef SIMDJSON_IMPLEMENTATION_PPC64
+#define SIMDJSON_IMPLEMENTATION_PPC64 (SIMDJSON_IS_PPC64)
+#endif
+
 #include "simdjson/internal/isadetection.h"
 #include "simdjson/internal/jsoncharutils_tables.h"
 #include "simdjson/internal/numberparsing_tables.h"