diff --git a/src/tint/reader/spirv/function.cc b/src/tint/reader/spirv/function.cc
index 45f6b35f4d..c3c12f2089 100644
--- a/src/tint/reader/spirv/function.cc
+++ b/src/tint/reader/spirv/function.cc
@@ -4075,6 +4075,12 @@ TypedExpression FunctionEmitter::EmitGlslStd450ExtInst(const spvtools::opt::Inst
     // All parameters to GLSL.std.450 extended instructions are IDs.
     for (uint32_t iarg = 2; iarg < inst.NumInOperands(); ++iarg) {
         TypedExpression operand = MakeOperand(inst, iarg);
+        if (!operand.expr) {
+            if (!failed()) {
+                Fail() << "unexpected failure to make an operand";
+            }
+            return {};
+        }
         if (first_operand_type == nullptr) {
             first_operand_type = operand.type;
         }
diff --git a/src/tint/reader/spirv/parser_impl.cc b/src/tint/reader/spirv/parser_impl.cc
index 6f6bf1e5a0..220ccb9f1e 100644
--- a/src/tint/reader/spirv/parser_impl.cc
+++ b/src/tint/reader/spirv/parser_impl.cc
@@ -1891,8 +1891,6 @@ TypedExpression ParserImpl::MakeConstantExpression(uint32_t id) {
     }
     auto source = GetSourceForInst(inst);
 
-    // TODO(dneto): Handle spec constants too?
-
     auto* original_ast_type = ConvertType(inst->type_id());
     if (original_ast_type == nullptr) {
         return {};
@@ -1952,6 +1950,12 @@ TypedExpression ParserImpl::MakeConstantExpression(uint32_t id) {
             declared_constant_composites_.insert({id, decl->name->symbol});
             return {original_ast_type, builder_.Expr(name)};
         }
+        case spv::Op::OpSpecConstantComposite:
+        case spv::Op::OpSpecConstantOp: {
+            // TODO(crbug.com/tint/111): Handle OpSpecConstantOp and OpSpecConstantComposite here.
+            Fail() << "unimplemented: OpSpecConstantOp and OpSpecConstantComposite";
+            return {};
+        }
         default:
             break;
     }