diff --git a/ext/mbstring/mbstring.c b/ext/mbstring/mbstring.c
index f3559e65b411..a9f6cd628292 100644
--- a/ext/mbstring/mbstring.c
+++ b/ext/mbstring/mbstring.c
@@ -4637,6 +4637,14 @@ MBSTRING_API bool php_mb_check_encoding(const char *input, size_t length, const
 	return true;
 }
 
+/* MSVC 32-bit has issues with 64-bit intrinsics.
+ * (Bad 7/8-byte UTF-8 strings would be wrongly passed through as 'valid')
+ * It seems this is caused by a bug in MS Visual C++
+ * Ref: https://stackoverflow.com/questions/37509129/potential-bug-in-visual-studio-c-compiler-or-in-intel-intrinsics-avx2-mm256-s */
+#if defined(PHP_WIN32) && !defined(__clang__) && defined(_MSC_VER) && defined(_M_IX86)
+# define MBSTRING_BROKEN_X86_MSVC_INTRINSICS
+#endif
+
 /* If we are building an AVX2-only binary, don't compile the next function */
 #ifndef ZEND_INTRIN_AVX2_NATIVE
 
@@ -4802,7 +4810,11 @@ static bool mb_fast_check_utf8_default(zend_string *str)
 			goto check_operand;
 		case 7:
 		case 8:
+#ifdef MBSTRING_BROKEN_X86_MSVC_INTRINSICS
+			operand = _mm_set_epi32(0, 0, ((int32_t*)p)[1], ((int32_t*)p)[0]);
+#else
 			operand = _mm_set_epi64x(0, *((uint64_t*)p));
+#endif
 			goto check_operand;
 		case 9:
 			operand = _mm_srli_si128(_mm_loadu_si128((__m128i*)(p - 6)), 6);
@@ -5195,12 +5207,11 @@ static bool mb_fast_check_utf8_avx2(zend_string *str)
 			goto check_operand;
 		case 7:
 		case 8:
-			/* This was originally: operand = _mm256_set_epi64x(0, 0, 0, *((int64_t*)p));
-			 * However, that caused test failures on 32-bit MS Windows
-			 * (Bad 7/8-byte UTF-8 strings would be wrongly passed through as 'valid')
-			 * It seems this is caused by a bug in MS Visual C++
-			 * Ref: https://stackoverflow.com/questions/37509129/potential-bug-in-visual-studio-c-compiler-or-in-intel-intrinsics-avx2-mm256-s */
+#ifdef MBSTRING_BROKEN_X86_MSVC_INTRINSICS
 			operand = _mm256_set_epi32(0, 0, 0, 0, 0, 0, ((int32_t*)p)[1], ((int32_t*)p)[0]);
+#else
+			operand = _mm256_set_epi64x(0, 0, 0, *((int64_t*)p));
+#endif
 			goto check_operand;
 		case 9:
 			operand = _mm256_set_m128i(_mm_setzero_si128(), _mm_srli_si128(_mm_loadu_si128((__m128i*)(p - 6)), 6));
diff --git a/ext/mbstring/tests/utf_encodings.phpt b/ext/mbstring/tests/utf_encodings.phpt
index 856f8ff08169..06c35b154652 100644
--- a/ext/mbstring/tests/utf_encodings.phpt
+++ b/ext/mbstring/tests/utf_encodings.phpt
@@ -5,9 +5,6 @@ mbstring
 --SKIPIF--
 <?php
 if (getenv("SKIP_SLOW_TESTS")) die("skip slow test");
-if (substr(PHP_OS, 0, 3) === 'WIN' && PHP_INT_SIZE === 4) {
-    die('xfail Fails on 32-bit Windows');
-}
 ?>
 --FILE--
 <?php