diff --git a/src/reader/spirv/parser_impl.cc b/src/reader/spirv/parser_impl.cc
index 7551a7a558..62d92a16b7 100644
--- a/src/reader/spirv/parser_impl.cc
+++ b/src/reader/spirv/parser_impl.cc
@@ -1166,7 +1166,13 @@ bool ParserImpl::EmitScalarSpecConstants() {
       ast::DecorationList spec_id_decos;
       for (const auto& deco : GetDecorationsFor(inst.result_id())) {
         if ((deco.size() == 2) && (deco[0] == SpvDecorationSpecId)) {
-          auto* cid = create<ast::OverrideDecoration>(Source{}, deco[1]);
+          const uint32_t id = deco[1];
+          if (id > 65535) {
+            return Fail() << "SpecId too large. WGSL override IDs must be "
+                             "between 0 and 65535: ID %"
+                          << inst.result_id() << " has SpecId " << id;
+          }
+          auto* cid = create<ast::OverrideDecoration>(Source{}, id);
           spec_id_decos.push_back(cid);
           break;
         }
diff --git a/src/reader/spirv/parser_impl_module_var_test.cc b/src/reader/spirv/parser_impl_module_var_test.cc
index cc6de3320a..984147cbda 100644
--- a/src/reader/spirv/parser_impl_module_var_test.cc
+++ b/src/reader/spirv/parser_impl_module_var_test.cc
@@ -2069,6 +2069,35 @@ TEST_F(
 })")) << module_str;
 }
 
+TEST_F(SpvModuleScopeVarParserTest, ScalarSpecConstant_DeclareConst_Id_TooBig) {
+  // Override IDs must be between 0 and 65535
+  auto p = parser(test::Assemble(Preamble() + FragMain() + R"(
+     OpDecorate %1 SpecId 65536
+     %bool = OpTypeBool
+     %1 = OpSpecConstantTrue %bool
+     %void = OpTypeVoid
+     %voidfn = OpTypeFunction %void
+  )" + MainBody()));
+  EXPECT_FALSE(p->Parse());
+  EXPECT_EQ(p->error(),
+            "SpecId too large. WGSL override IDs must be between 0 and 65535: "
+            "ID %1 has SpecId 65536");
+}
+
+TEST_F(SpvModuleScopeVarParserTest,
+       ScalarSpecConstant_DeclareConst_Id_MaxValid) {
+  // Override IDs must be between 0 and 65535
+  auto p = parser(test::Assemble(Preamble() + FragMain() + R"(
+     OpDecorate %1 SpecId 65535
+     %bool = OpTypeBool
+     %1 = OpSpecConstantTrue %bool
+     %void = OpTypeVoid
+     %voidfn = OpTypeFunction %void
+  )" + MainBody()));
+  EXPECT_TRUE(p->Parse());
+  EXPECT_EQ(p->error(), "");
+}
+
 TEST_F(SpvModuleScopeVarParserTest, ScalarSpecConstant_DeclareConst_True) {
   auto p = parser(test::Assemble(Preamble() + FragMain() + R"(
      OpName %c "myconst"