diff --git a/mlir/examples/toy/Ch2/mlir/Dialect.cpp b/mlir/examples/toy/Ch2/mlir/Dialect.cpp
--- a/mlir/examples/toy/Ch2/mlir/Dialect.cpp
+++ b/mlir/examples/toy/Ch2/mlir/Dialect.cpp
@@ -111,13 +111,27 @@
 /// similarly to the `build` methods described above.
 mlir::ParseResult ConstantOp::parse(mlir::OpAsmParser &parser,
                                     mlir::OperationState &result) {
-  mlir::DenseElementsAttr value;
-  if (parser.parseOptionalAttrDict(result.attributes) ||
-      parser.parseAttribute(value, "value", result.attributes))
-    return failure();
+  if (parser.parseOptionalAttrDict(result.attributes)) {
+    return mlir::failure();
+  }
+
+  auto attributes = result.attributes.getAttrs();
+  if (attributes.size() != 1) {
+    return mlir::failure();
+  }
+
+  auto attribute = attributes.front();
+  if (attribute.getName() != "value") {
+    return mlir::failure();
+  }
+
+  auto value = attribute.getValue().dyn_cast<mlir::DenseElementsAttr>();
+  if (!value) {
+    return mlir::failure();
+  }
 
   result.addTypes(value.getType());
-  return success();
+  return mlir::success();
 }
 
 /// The 'OpAsmPrinter' class is a stream that allows for formatting
diff --git a/mlir/test/Examples/Toy/Ch2/constant.mlir b/mlir/test/Examples/Toy/Ch2/constant.mlir
new file mode 100644
--- /dev/null
+++ b/mlir/test/Examples/Toy/Ch2/constant.mlir
@@ -0,0 +1,7 @@
+// RUN: toyc-ch2 %s -emit=mlir 2>&1
+
+toy.func @single_constant() -> tensor<*xf64> {
+  %0 = toy.constant {value = dense<[0.]> : tensor<1xf64>}
+  // CHECK: toy.constant {value = dense<[0.000000e+00] : tensor<1xf64}
+  toy.return %0 : tensor<1xf64>
+}