diff --git a/BizHawk.MultiClient/movie/Movie.cs b/BizHawk.MultiClient/movie/Movie.cs
index 2acf7abdb0..fcc44c918d 100644
--- a/BizHawk.MultiClient/movie/Movie.cs
+++ b/BizHawk.MultiClient/movie/Movie.cs
@@ -338,7 +338,7 @@ namespace BizHawk.MultiClient
 
         public void SetHeaderLine(string key, string value)
         {
-            Header.AddHeaderLine(key, value);
+            Header.SetHeaderLine(key, value);
         }
 
         public string GetTime()
diff --git a/BizHawk.MultiClient/movie/MovieHeader.cs b/BizHawk.MultiClient/movie/MovieHeader.cs
index e8ac3b9550..ed3bbdd027 100644
--- a/BizHawk.MultiClient/movie/MovieHeader.cs
+++ b/BizHawk.MultiClient/movie/MovieHeader.cs
@@ -53,7 +53,10 @@ namespace BizHawk.MultiClient
         /// <param name="value"></param>
         public void AddHeaderLine(string key, string value)
         {
-            HeaderParams.Add(key, value);
+            string temp = value;
+
+            if(!HeaderParams.TryGetValue(key, out temp)) //TODO: does a failed attempt mess with value?
+                HeaderParams.Add(key, value);
         }
 
         public void UpdateRerecordCount(int count)
@@ -77,5 +80,10 @@ namespace BizHawk.MultiClient
             HeaderParams.TryGetValue(key, out value);
             return value;
         }
+
+        public void SetHeaderLine(string key, string value)
+        {
+            HeaderParams[key] = value;
+        }
     }
 }