diff --git a/src/compatibility.cpp b/src/compatibility.cpp
index 80532c788..6933a449d 100644
--- a/src/compatibility.cpp
+++ b/src/compatibility.cpp
@@ -74,7 +74,8 @@ enum
 	CP_END,
 	CP_CLEARFLAGS,
 	CP_SETFLAGS,
-	CP_SETSPECIAL
+	CP_SETSPECIAL,
+	CP_SETACTIVATION
 };
 
 // EXTERNAL FUNCTION PROTOTYPES --------------------------------------------
@@ -239,6 +240,15 @@ void ParseCompatibility()
 					CompatParams.Push(sc.Number);
 				}
 			}
+			else if (sc.Compare("setactivation"))
+			{
+				if (flags.ExtCommandIndex == ~0u) flags.ExtCommandIndex = CompatParams.Size();
+				CompatParams.Push(CP_SETACTIVATION);
+				sc.MustGetNumber();
+				CompatParams.Push(sc.Number);
+				sc.MustGetNumber();
+				CompatParams.Push(sc.Number);
+			}
 			else 
 			{
 				sc.UnGet();
@@ -388,6 +398,16 @@ void SetCompatibilityParams()
 					i+=8;
 					break;
 				}
+				case CP_SETACTIVATION:
+				{
+					if (CompatParams[i+1] < numlines)
+					{
+						line_t *line = &lines[CompatParams[i+1]];
+						line->activation = CompatParams[i+2];
+					}
+					i += 3;
+					break;
+				}
 			}
 		}
 	}
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 0dcac898a..e78dd99ea 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -5293,8 +5293,11 @@ int DLevelScript::RunScript ()
 			break;
 
 		case PCD_CLEARLINESPECIAL:
-			if (activationline)
+			if (activationline != NULL)
+			{
 				activationline->special = 0;
+				DPrintf("Cleared line special on line %d\n", activationline - lines);
+			}
 			break;
 
 		case PCD_CASEGOTO:
@@ -5931,6 +5934,8 @@ int DLevelScript::RunScript ()
 					line->args[2] = STACK(3);
 					line->args[3] = STACK(2);
 					line->args[4] = STACK(1);
+					DPrintf("Set special on line %d (id %d) to %d(%d,%d,%d,%d,%d)\n",
+						linenum, STACK(7), specnum, arg0, STACK(4), STACK(3), STACK(2), STACK(1));
 				}
 				sp -= 7;
 			}
diff --git a/wadsrc/static/compatibility.txt b/wadsrc/static/compatibility.txt
index 2a8a40211..21a907992 100644
--- a/wadsrc/static/compatibility.txt
+++ b/wadsrc/static/compatibility.txt
@@ -148,3 +148,11 @@ DCE862393CAAA6FF1294FB7056B53057 // UAC Ultra map07: Contains a scroller dependi
 {
 	badangles
 }
+
+E2B5D1400279335811C1C1C0B437D9C8 // Deathknights of the Dark Citidel, map54
+{
+	// This map has two gear boxes which are flagged for player cross
+	// activation instead of the proper player uses activation.
+	setactivation 963 2
+	setactivation 943 2
+}