diff --git a/source/val/validate_builtins.cpp b/source/val/validate_builtins.cpp
index f9b29dd04c..89bd49ef57 100644
--- a/source/val/validate_builtins.cpp
+++ b/source/val/validate_builtins.cpp
@@ -3218,17 +3218,20 @@ spv_result_t BuiltInsValidator::ValidateI32Vec4InputAtDefinition(
 
 spv_result_t BuiltInsValidator::ValidateWorkgroupSizeAtDefinition(
     const Decoration& decoration, const Instruction& inst) {
-  if (spv_result_t error = ValidateI32Vec(
-          decoration, inst, 3,
-          [this, &inst](const std::string& message) -> spv_result_t {
-            return _.diag(SPV_ERROR_INVALID_DATA, &inst)
-                   << _.VkErrorID(4427) << "According to the "
-                   << spvLogStringForEnv(_.context()->target_env)
-                   << " spec BuiltIn WorkgroupSize variable needs to be a "
-                      "3-component 32-bit int vector. "
-                   << message;
-          })) {
-    return error;
+  // Vulkan requires 32-bit int, but Universal has no restrictions
+  if (spvIsVulkanEnv(_.context()->target_env)) {
+    if (spv_result_t error = ValidateI32Vec(
+            decoration, inst, 3,
+            [this, &inst](const std::string& message) -> spv_result_t {
+              return _.diag(SPV_ERROR_INVALID_DATA, &inst)
+                     << _.VkErrorID(4427) << "According to the "
+                     << spvLogStringForEnv(_.context()->target_env)
+                     << " spec BuiltIn WorkgroupSize variable needs to be a "
+                        "3-component 32-bit int vector. "
+                     << message;
+            })) {
+      return error;
+    }
   }
 
   if (!spvOpcodeIsConstant(inst.opcode())) {
diff --git a/test/val/val_modes_test.cpp b/test/val/val_modes_test.cpp
index ecde2457ca..6bd6e8ed99 100644
--- a/test/val/val_modes_test.cpp
+++ b/test/val/val_modes_test.cpp
@@ -318,6 +318,37 @@ OpExecutionModeId %main LocalSizeId %int_1 %int_0 %int_1
           "Local Size Id execution mode must not have a product of zero"));
 }
 
+// https://github.com/KhronosGroup/SPIRV-Tools/issues/5939
+TEST_F(ValidateMode, KernelZeroLocalSize64) {
+  const std::string spirv = R"(
+               OpCapability Kernel
+               OpCapability Addresses
+               OpCapability Int64
+               OpCapability Linkage
+               OpMemoryModel Physical64 OpenCL
+               OpEntryPoint Kernel %test "test" %__spirv_BuiltInWorkgroupSize
+               OpExecutionMode %test ContractionOff
+               OpDecorate %__spirv_BuiltInWorkgroupSize Constant
+               OpDecorate %__spirv_BuiltInWorkgroupSize LinkageAttributes "__spirv_BuiltInWorkgroupSize" Import
+               OpDecorate %__spirv_BuiltInWorkgroupSize BuiltIn WorkgroupSize
+       %void = OpTypeVoid
+      %ulong = OpTypeInt 64 0
+    %v3ulong = OpTypeVector %ulong 3
+%_ptr_Input_v3ulong = OpTypePointer Input %v3ulong
+          %8 = OpTypeFunction %void
+%__spirv_BuiltInWorkgroupSize = OpVariable %_ptr_Input_v3ulong Input
+       %test = OpFunction %void None %8
+      %entry = OpLabel
+         %11 = OpLoad %v3ulong %__spirv_BuiltInWorkgroupSize Aligned 1
+         %12 = OpCompositeExtract %ulong %11 0
+               OpReturn
+               OpFunctionEnd
+)";
+
+  CompileSuccessfully(spirv);
+  EXPECT_EQ(SPV_SUCCESS, ValidateInstructions());
+}
+
 TEST_F(ValidateMode, FragmentOriginLowerLeftVulkan) {
   const std::string spirv = R"(
 OpCapability Shader