diff --git a/stl/inc/xutility b/stl/inc/xutility
index 14273a50119..49a64d2576c 100644
--- a/stl/inc/xutility
+++ b/stl/inc/xutility
@@ -58,10 +58,12 @@ _STL_DISABLE_CLANG_WARNINGS
 // In the STL's implementation, we inspect the following detection macros,
 // because various algorithms are vectorized for various architectures.
 
+// _CALL_ALL_X64_VECTOR_ALGORITHMS_ON_ARM64EC is a macro to test ARM64EC fallbacks for x64 algorithms.
+
 #if !_USE_STD_VECTOR_ALGORITHMS
 #define _VECTORIZED_FOR_X64_X86               0
 #define _VECTORIZED_FOR_X64_X86_ARM64_ARM64EC 0
-#elif defined(_M_ARM64) || defined(_M_ARM64EC)
+#elif defined(_M_ARM64) || (defined(_M_ARM64EC) && !defined(_CALL_ALL_X64_VECTOR_ALGORITHMS_ON_ARM64EC))
 #define _VECTORIZED_FOR_X64_X86               0
 #define _VECTORIZED_FOR_X64_X86_ARM64_ARM64EC 1
 #elif defined(_M_X64) || defined(_M_IX86)
diff --git a/tests/std/tests/VSO_0000000_vector_algorithms/env.lst b/tests/std/tests/VSO_0000000_vector_algorithms/env.lst
index 78fbe6b49a4..7a36bdceb04 100644
--- a/tests/std/tests/VSO_0000000_vector_algorithms/env.lst
+++ b/tests/std/tests/VSO_0000000_vector_algorithms/env.lst
@@ -5,3 +5,4 @@ RUNALL_INCLUDE ..\usual_matrix.lst
 RUNALL_CROSSLIST
 *	PM_CL=""
 *	PM_CL="/D_USE_STD_VECTOR_ALGORITHMS=0"
+*	PM_CL="/D_CALL_ALL_X64_VECTOR_ALGORITHMS_ON_ARM64EC"
diff --git a/tests/utils/stl/test/tests.py b/tests/utils/stl/test/tests.py
index 44d89d5ed97..af2e09d0bfa 100644
--- a/tests/utils/stl/test/tests.py
+++ b/tests/utils/stl/test/tests.py
@@ -316,6 +316,8 @@ def _parseFlags(self, litConfig):
                 self.requires.append('edg') # available for x64, see features.py
             elif flag[1:] == 'arch:AVX2':
                 self.requires.append('arch_avx2') # available for x86 and x64, see features.py
+            elif flag[1:] == 'D_CALL_ALL_X64_VECTOR_ALGORITHMS_ON_ARM64EC':
+                self.requires.append('arm64ec')
             elif flag[1:] == 'MDd':
                 self._addCustomFeature('MDd')
                 self._addCustomFeature('debug_CRT')