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
@@ -220,6 +220,11 @@
     parser.emitError(loc) << "expected non empty string in !emitc.opaque type";
     return Type();
   }
+  if (value.find("*") != std::string::npos) {
+    parser.emitError(loc)
+        << "* not allowed in !emitc.opaque type, use !emitc.ptr instead";
+    return Type();
+  }
   if (parser.parseGreater())
     return Type();
   return get(parser.getContext(), value);
diff --git a/mlir/test/Dialect/EmitC/invalid_types.mlir b/mlir/test/Dialect/EmitC/invalid_types.mlir
--- a/mlir/test/Dialect/EmitC/invalid_types.mlir
+++ b/mlir/test/Dialect/EmitC/invalid_types.mlir
@@ -4,3 +4,10 @@
     // expected-error @+1 {{expected non empty string in !emitc.opaque type}}
     %1 = "emitc.variable"(){value = "42" : !emitc.opaque<"">} : () -> !emitc.opaque<"mytype">
 }
+
+// -----
+
+func @illegal_opaque_type_2() {
+    // expected-error @+1 {{* not allowed in !emitc.opaque type, use !emitc.ptr instead}}
+    %1 = "emitc.variable"(){value = "nullptr" : !emitc.opaque<"int32_t*">} : () -> !emitc.opaque<"int32_t*">
+}