diff --git a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
--- a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
+++ b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
@@ -1205,10 +1205,9 @@
     return op.emitOpError() << "requires attribute's type (" << value.getType()
                             << ") to match op's return type (" << type << ")";
 
-  if (type.isa<IndexType>() || value.isa<BoolAttr>())
-    return success();
-
   if (auto intAttr = value.dyn_cast<IntegerAttr>()) {
+    if (type.isa<IndexType>() || value.isa<BoolAttr>())
+      return success();
     IntegerType intType = type.cast<IntegerType>();
     if (!intType.isSignless())
       return op.emitOpError("requires integer result types to be signless");
diff --git a/mlir/test/Dialect/Standard/invalid.mlir b/mlir/test/Dialect/Standard/invalid.mlir
--- a/mlir/test/Dialect/Standard/invalid.mlir
+++ b/mlir/test/Dialect/Standard/invalid.mlir
@@ -247,3 +247,11 @@
   %0 = constant 0 : si32
   return
 }
+
+// -----
+
+func @unsupported_attribute() {
+  // expected-error @+1 {{unsupported 'value' attribute: "" : index}}
+  %0 = constant "" : index
+  return
+}