diff --git a/crypto/internal.h b/crypto/internal.h
index 3bfeaf7a78..62ce4a3271 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -206,10 +206,18 @@ typedef __uint128_t uint128_t;
 #define OPENSSL_SSE2
 #endif
 
-// For convenience in testing 64-bit generic code, we allow disabling SSE2
-// intrinsics via |OPENSSL_NO_SSE2_FOR_TESTING|. x86_64 always has SSE2
-// available, so we would otherwise need to test such code on a non-x86_64
-// platform.
+#if defined(OPENSSL_X86) && !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_SSE2)
+#error \
+    "x86 assembly requires SSE2. Build with -msse2 (recommended), or disable assembly optimizations with -DOPENSSL_NO_ASM."
+#endif
+
+// For convenience in testing the fallback code, we allow disabling SSE2
+// intrinsics via |OPENSSL_NO_SSE2_FOR_TESTING|. We require SSE2 on x86 and
+// x86_64, so we would otherwise need to test such code on a non-x86 platform.
+//
+// This does not remove the above requirement for SSE2 support with assembly
+// optimizations. It only disables some intrinsics-based optimizations so that
+// we can test the fallback code on CI.
 #if defined(OPENSSL_SSE2) && defined(OPENSSL_NO_SSE2_FOR_TESTING)
 #undef OPENSSL_SSE2
 #endif