diff --git a/Build/Configurations/Includes/ZDoom_common.cfg b/Build/Configurations/Includes/ZDoom_common.cfg
index 40d67a7..ad8b12f 100644
--- a/Build/Configurations/Includes/ZDoom_common.cfg
+++ b/Build/Configurations/Includes/ZDoom_common.cfg
@@ -33,6 +33,9 @@ common
 	defaulttexturescale = 1.0f;
 	defaultflatscale = 1.0f;
 	scaledtextureoffsets = true;
+	
+	//mxd. Sidedefs compression
+	sidedefcompressionignoresaction = true;
 
 	// Texture sources
 	textures
diff --git a/Help/gc_basicsettings.html b/Help/gc_basicsettings.html
index 6a6904c..914f5d3 100644
--- a/Help/gc_basicsettings.html
+++ b/Help/gc_basicsettings.html
@@ -145,10 +145,15 @@ defaultskytextures
 	SKY3 = "MAP21,MAP22,MAP23,MAP24,MAP25";
 }
 </pre>
-		<br />
-<b class="fat">longtexturenames</b> (boolean) - <span class="red">GZDB only</span>.<br />
-		Enables support for long (> 8 chars) texture names. This is used by GZDoom Builder to limit the input fields in the user interface and to check the validity of texture names in resources. This setting should only be enabled for UDMF game configurations. Enabling this setting will make maps incompatible with Doom Builder 2 and can lead to problems in Slade 3 This does NOT determine the actual limitation on the texture names in the map file format.<br />Default value is <b>false</b>.<br />
-		<br />
+	<br />
+	<b class="fat">longtexturenames</b> (boolean) - <span class="red">GZDB only</span>.<br />
+	Enables support for long (> 8 chars) texture names. This is used by GZDoom Builder to limit the input fields in the user interface and to check the validity of texture names in resources. This setting should only be enabled for UDMF game configurations. Enabling this setting will make maps incompatible with Doom Builder 2 and can lead to problems in Slade 3 This does NOT determine the actual limitation on the texture names in the map file format.<br />
+	Default value is <b>false</b>.<br />
+	<br />
+    <b class="fat">sidedefcompressionignoresaction</b> (boolean) - <span class="red">GZDB only</span>.<br />
+    When set to true, sidedefs will be compressed regardless of linedef action (DB2 behaviour, can potentially cause problems when target source port doesn't decompress sidedefs).<br />
+    When set to false, sidedefs, which belong to a line with an action, will be skipped when compressing sidedefs.<br />
+    Default value is <b>false</b>.<br />
 	</p>
 	</div>
 </body>
diff --git a/Source/Core/Config/GameConfiguration.cs b/Source/Core/Config/GameConfiguration.cs
index c34f85f..f0806d9 100644
--- a/Source/Core/Config/GameConfiguration.cs
+++ b/Source/Core/Config/GameConfiguration.cs
@@ -88,6 +88,7 @@ namespace CodeImp.DoomBuilder.Config
 		private readonly bool doomlightlevels;
 		private readonly string actionspecialhelp; //mxd
 		private readonly string thingclasshelp; //mxd
+		private readonly bool sidedefcompressionignoresaction; //mxd
 		
 		// Skills
 		private readonly List<SkillInfo> skills;
@@ -214,6 +215,7 @@ namespace CodeImp.DoomBuilder.Config
 		public bool DoomLightLevels { get { return doomlightlevels; } }
 		public string ActionSpecialHelp { get { return actionspecialhelp; } } //mxd
 		public string ThingClassHelp { get { return thingclasshelp; } } //mxd
+		internal bool SidedefCompressionIgnoresAction { get { return sidedefcompressionignoresaction; } } //mxd
 
 		// Skills
 		public List<SkillInfo> Skills { get { return skills; } }
@@ -371,6 +373,7 @@ namespace CodeImp.DoomBuilder.Config
 			doomlightlevels = cfg.ReadSetting("doomlightlevels", true);
 			actionspecialhelp = cfg.ReadSetting("actionspecialhelp", string.Empty); //mxd
 			thingclasshelp = cfg.ReadSetting("thingclasshelp", string.Empty); //mxd
+			sidedefcompressionignoresaction = cfg.ReadSetting("sidedefcompressionignoresaction", false); //mxd
 			defaultLinedefActivation = cfg.ReadSetting("defaultlinedefactivation", ""); //mxd
 			for(int i = 0; i < Linedef.NUM_ARGS; i++) makedoorargs[i] = cfg.ReadSetting("makedoorarg" + i.ToString(CultureInfo.InvariantCulture), 0);
 
diff --git a/Source/Core/Map/MapSet.cs b/Source/Core/Map/MapSet.cs
index f5cd4ff..b1563ec 100644
--- a/Source/Core/Map/MapSet.cs
+++ b/Source/Core/Map/MapSet.cs
@@ -3211,6 +3211,14 @@ namespace CodeImp.DoomBuilder.Map
 				Sidedef stored = null;
 				Sidedef snsd = sidedefs[sn];
 
+				//mxd. Skip sidedef if it belongs to a linedef with an action?
+				if(!General.Map.Config.SidedefCompressionIgnoresAction && snsd.Line.Action != 0)
+				{
+					// Next!
+					sn++;
+					continue;
+				}
+
 				// Check if checksum is stored
 				bool samesidedef = false;
 				uint checksum = snsd.GetChecksum();