diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ObjectWriter.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ObjectWriter.cs
index 18e9e2b90221e7ad82571d3d4f98ddb7ecbca870..9e5cfcc0ea10868ae880518197fc6f8960a651f9 100644
--- a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ObjectWriter.cs
+++ b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ObjectWriter.cs
@@ -80,7 +80,7 @@ public class ObjectWriter : IDisposable, ITypesDebugInfoWriter
 #endif
 
         [DllImport(NativeObjectWriterFileName)]
-        private static extern IntPtr InitObjWriter(string objectFilePath, string triple = null);
+        private static extern IntPtr InitObjWriter([MarshalAs(UnmanagedType.LPUTF8Str)] string objectFilePath, string triple = null);
 
         [DllImport(NativeObjectWriterFileName)]
         private static extern void FinishObjWriter(IntPtr objWriter);