diff --git a/mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp b/mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp
--- a/mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp
+++ b/mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp
@@ -49,6 +49,8 @@
   // LLVM container types may (recursively) contain other types that must be
   // converted even when the outer type is compatible.
   addConversion([&](LLVM::LLVMPointerType type) -> llvm::Optional<Type> {
+    if (type.isOpaque())
+      return type;
     if (auto pointee = convertType(type.getElementType()))
       return LLVM::LLVMPointerType::get(pointee, type.getAddressSpace());
     return llvm::None;
diff --git a/mlir/test/Conversion/FuncToLLVM/convert-types.mlir b/mlir/test/Conversion/FuncToLLVM/convert-types.mlir
--- a/mlir/test/Conversion/FuncToLLVM/convert-types.mlir
+++ b/mlir/test/Conversion/FuncToLLVM/convert-types.mlir
@@ -4,6 +4,11 @@
 // CHECK: !llvm.ptr<i42>
 func.func private @ptr() -> !llvm.ptr<!test.smpla>
 
+// CHECK-LABEL: @opaque_ptr
+// CHECK: !llvm.ptr
+// CHECK-NOT: <
+func.func private @opaque_ptr() -> !llvm.ptr
+
 // CHECK-LABEL: @ptr_ptr()
 // CHECK: !llvm.ptr<ptr<i42>> 
 func.func private @ptr_ptr() -> !llvm.ptr<!llvm.ptr<!test.smpla>>