diff --git a/GameData/ROEngines/PartConfigs/Castor4_BDB.cfg b/GameData/ROEngines/PartConfigs/Castor4_BDB.cfg
index 6264776b..cf4e75ba 100644
--- a/GameData/ROEngines/PartConfigs/Castor4_BDB.cfg
+++ b/GameData/ROEngines/PartConfigs/Castor4_BDB.cfg
@@ -130,3 +130,11 @@ PART
 		}
 	}
 }
+
+// The -4A has the same casing as the -4, but a slightly bigger nozzle.
++PART[ROE-Castor4]
+{
+	@name = ROE-Castor4A
+	@engineType = Castor-4A
+	@tags = castor, castor-4a, 4a, iva, castor-iva, delta, atlas, booster, radial, solid, srb, castor4a
+}
diff --git a/GameData/ROEngines/PatchManager/ActiveMMPatches/Castor-4A.cfg b/GameData/ROEngines/PatchManager/ActiveMMPatches/Castor-4A.cfg
new file mode 100644
index 00000000..df836077
--- /dev/null
+++ b/GameData/ROEngines/PatchManager/ActiveMMPatches/Castor-4A.cfg
@@ -0,0 +1 @@
+!PART:HAS[~name[ROE-*]&#engineType[Castor-4A]&#category[Engine]]:BEFORE[zzzTagCleanup] {}
diff --git a/GameData/ROEngines/PatchManager/ROE-PatchManager.cfg b/GameData/ROEngines/PatchManager/ROE-PatchManager.cfg
index e106cbae..34289cee 100644
--- a/GameData/ROEngines/PatchManager/ROE-PatchManager.cfg
+++ b/GameData/ROEngines/PatchManager/ROE-PatchManager.cfg
@@ -233,6 +233,15 @@ PatchManager
  installedWithMod = True
 }
 PatchManager
+{
+ modName = ROEngines
+ srcPath = ROEngines/PatchManager/PluginData/Castor-4A.cfg
+ patchName = Castor-4A
+ shortDescr = Castor-4A
+ longDescr = Removes the duplicated Castor-4A engines from other mods.
+ installedWithMod = True
+}
+PatchManager
 {
  modName = ROEngines
  srcPath = ROEngines/PatchManager/PluginData/Castor-4AXL.cfg
diff --git a/GameData/ROEngines/RealPlume/Castor4_BDB_RealPlume.cfg b/GameData/ROEngines/RealPlume/Castor4_BDB_RealPlume.cfg
index 8536ab04..9699f873 100644
--- a/GameData/ROEngines/RealPlume/Castor4_BDB_RealPlume.cfg
+++ b/GameData/ROEngines/RealPlume/Castor4_BDB_RealPlume.cfg
@@ -1,4 +1,4 @@
-@PART[ROE-Castor4|ROE-Castor4AXL]:BEFORE[RealPlume]
+@PART[ROE-Castor4|ROE-Castor4A|ROE-Castor4AXL]:BEFORE[RealPlume]
 {
 	PLUME
 	{
diff --git a/GameData/ROEngines/Waterfall/SRM/EarlyCastors.cfg b/GameData/ROEngines/Waterfall/SRM/EarlyCastors.cfg
index 85808306..0222d1b1 100644
--- a/GameData/ROEngines/Waterfall/SRM/EarlyCastors.cfg
+++ b/GameData/ROEngines/Waterfall/SRM/EarlyCastors.cfg
@@ -37,7 +37,7 @@
         glow = ro-srm
     }
 }
-@PART[ROE-Castor4|ROE-Castor4AXL]:BEFORE[ROWaterfall]:NEEDS[Waterfall,SmokeScreen]
+@PART[ROE-Castor4|ROE-Castor4A|ROE-Castor4AXL]:BEFORE[ROWaterfall]:NEEDS[Waterfall,SmokeScreen]
 {
     ROWaterfall
     {