diff --git a/ShellUnresponsiveException.cs b/ShellUnresponsiveException.cs
index 78c3c22..3bd7101 100644
--- a/ShellUnresponsiveException.cs
+++ b/ShellUnresponsiveException.cs
@@ -6,9 +6,9 @@ public class ShellUnresponsiveException: Exception
         const string DefaultMessage = "Shell is unresponsive";
 
         public ShellUnresponsiveException() : base(DefaultMessage) { }
-        public ShellUnresponsiveException(string message, Exception innerException)
+        public ShellUnresponsiveException(string message, Exception? innerException)
             : base(message, innerException) { }
-        public ShellUnresponsiveException(Exception innerException)
+        public ShellUnresponsiveException(Exception? innerException)
             : base(DefaultMessage, innerException: innerException) { }
     }
 }
diff --git a/WindowNotFoundException.cs b/WindowNotFoundException.cs
index 854061d..cf547a7 100644
--- a/WindowNotFoundException.cs
+++ b/WindowNotFoundException.cs
@@ -7,10 +7,10 @@ public class WindowNotFoundException: Exception
 
         public WindowNotFoundException() : base(DefaultMessage) { }
 
-        public WindowNotFoundException(string message, Exception innerException):
+        public WindowNotFoundException(string message, Exception? innerException):
             base(message, innerException) { }
 
-        public WindowNotFoundException(Exception innerException):
+        public WindowNotFoundException(Exception? innerException):
             base(DefaultMessage, innerException: innerException) { }
     }
 }