diff -rauN a/mozglue/misc/SIMD_avx2.cpp b/mozglue/misc/SIMD_avx2.cpp
--- a/mozglue/misc/SIMD_avx2.cpp	2022-10-24 18:34:51.028779452 +0200
+++ b/mozglue/misc/SIMD_avx2.cpp	2022-10-24 18:35:07.818868490 +0200
@@ -8,6 +8,7 @@
 #include "mozilla/SSE.h"
 #include "mozilla/Assertions.h"
 
+#undef MOZILLA_MAY_SUPPORT_AVX2
 #ifdef MOZILLA_MAY_SUPPORT_AVX2
 
 #  include <cstring>