diff --git a/src/p_map.cpp b/src/p_map.cpp
index 233cc50cd..68d0b21f0 100644
--- a/src/p_map.cpp
+++ b/src/p_map.cpp
@@ -887,6 +887,20 @@ bool PIT_CheckLine(line_t *ld, const FBoundingBox &box, FCheckPosition &tm)
 	return true;
 }
 
+
+//==========================================================================
+//
+// Isolated to keep the code readable and fix the logic
+//
+//==========================================================================
+
+static bool CheckRipLevel(AActor *victim, AActor *projectile)
+{
+	if (victim->RipLevelMin > 0 && projectile->RipperLevel < victim->RipLevelMin) return false;
+	if (victim->RipLevelMax > 0 && projectile->RipperLevel > victim->RipLevelMax) return false;
+	return true;
+}
+
 //==========================================================================
 //
 // PIT_CheckThing
@@ -1207,17 +1221,8 @@ bool PIT_CheckThing(AActor *thing, FCheckPosition &tm)
 		{
 			return true;
 		}
-		// Rippers will rip through anything with an equivalent ripper level,
-		// or if the missile's ripper level is within the min/max range,
-		// or if there's no min/max range and the missile's ripper level is
-		// >= the monster's, then let 'er rip!
-		bool ripmin = (thing->RipLevelMin != 0) ? true : false;
-		bool ripmax = (thing->RipLevelMax != 0) ? true : false;
-		if ((tm.DoRipping && !(thing->flags5 & MF5_DONTRIP)) && 
-			((!(ripmin) && !(ripmax) && (thing->RipperLevel <= tm.thing->RipperLevel)) ||
-			((thing->RipperLevel == tm.thing->RipperLevel) ||
-			(thing->RipLevelMin <= tm.thing->RipperLevel) &&
-			(thing->RipLevelMax >= tm.thing->RipperLevel))))
+
+		if ((tm.DoRipping && !(thing->flags5 & MF5_DONTRIP)) && CheckRipLevel(thing, tm.thing))
 		{
 			if (!(tm.thing->flags6 & MF6_NOBOSSRIP) || !(thing->flags2 & MF2_BOSS))
 			{
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index a00ac62e1..677979276 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -1442,6 +1442,10 @@ DEFINE_PROPERTY(telefogdesttype, S, Actor)
 DEFINE_PROPERTY(ripperlevel, I, Actor)
 {
 	PROP_INT_PARM(id, 0);
+	if (id < 0)
+	{
+		I_Error ("RipperLevel must not be negative");
+	}
 	defaults->RipperLevel = id;
 }
 
@@ -1451,6 +1455,10 @@ DEFINE_PROPERTY(ripperlevel, I, Actor)
 DEFINE_PROPERTY(riplevelmin, I, Actor)
 {
 	PROP_INT_PARM(id, 0);
+	if (id < 0)
+	{
+		I_Error ("RipLevelMin must not be negative");
+	}
 	defaults->RipLevelMin = id;
 }
 
@@ -1460,6 +1468,10 @@ DEFINE_PROPERTY(riplevelmin, I, Actor)
 DEFINE_PROPERTY(riplevelmax, I, Actor)
 {
 	PROP_INT_PARM(id, 0);
+	if (id < 0)
+	{
+		I_Error ("RipLevelMax must not be negative");
+	}
 	defaults->RipLevelMax = id;
 }