diff --git a/mlir/lib/Dialect/EmitC/IR/EmitC.cpp b/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
--- a/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
+++ b/mlir/lib/Dialect/EmitC/IR/EmitC.cpp
@@ -217,7 +217,7 @@
   std::string value;
   SMLoc loc = parser.getCurrentLocation();
   if (parser.parseOptionalString(&value) || value.empty()) {
-    parser.emitError(loc) << "expected non empty string";
+    parser.emitError(loc) << "expected non empty string in !emitc.opaque type";
     return Type();
   }
   if (parser.parseGreater())
diff --git a/mlir/test/Dialect/EmitC/invalid_types.mlir b/mlir/test/Dialect/EmitC/invalid_types.mlir
new file mode 100644
--- /dev/null
+++ b/mlir/test/Dialect/EmitC/invalid_types.mlir
@@ -0,0 +1,6 @@
+// RUN: mlir-opt %s -split-input-file -verify-diagnostics
+
+func @illegal_opaque_type_1() {
+    // expected-error @+1 {{expected non empty string in !emitc.opaque type}}
+    %1 = "emitc.variable"(){value = "42" : !emitc.opaque<"">} : () -> !emitc.opaque<"mytype">
+}