Index: sexp.cpp
===================================================================
--- sexp.cpp	(revision 10726)
+++ sexp.cpp	(working copy)
@@ -14911,9 +14911,7 @@
 	ship_subsys *ptr;
 
 	z = ship_query_state(CTEXT(node));
-	if (z == 1){
-		return SEXP_KNOWN_FALSE;  // ship isn't around, nor will it ever be
-	} else if (z == -1) {
+	if (z == 1 || z == -1) {
 		return SEXP_CANT_EVAL;
 	}
 

Index: sexp.cpp
===================================================================
--- sexp.cpp	(revision 10739)
+++ sexp.cpp	(working copy)
@@ -8468,13 +8468,13 @@
 		// only eval this argument if it's valid
 		if (Sexp_nodes[n].flags & SNF_ARGUMENT_VALID)
 		{
-			// flush conditional to avoid short-circuiting
-			flush_sexp_tree(condition_node);
-
 			// evaluate conditional for current argument
 			Sexp_replacement_arguments.push_back(Sexp_nodes[n].text);
 			val = eval_sexp(condition_node);
 
+			// flush conditional to avoid short-circuiting
+			flush_sexp_tree(condition_node);
+
 			switch (val)
 			{
 				case SEXP_TRUE:
@@ -8542,13 +8542,13 @@
 	{
 		// since we can't see or modify the validity, assume all are valid
 		{
-			// flush conditional to avoid short-circuiting
-			flush_sexp_tree(condition_node);
-
 			// evaluate conditional for current argument
 			Sexp_replacement_arguments.push_back(argument_vector[i]);
 			val = eval_sexp(condition_node);
 
+			// flush conditional to avoid short-circuiting
+			flush_sexp_tree(condition_node);
+
 			switch (val)
 			{
 				case SEXP_TRUE:
@@ -8741,12 +8741,14 @@
 	{
 		// flush stuff
 		Sexp_applicable_argument_list.clear_nesting_level();
-		flush_sexp_tree(condition_node);
 
 		// evaluate conditional for current argument
 		Sexp_replacement_arguments.push_back(Sexp_nodes[n].text);
 		val = eval_sexp(condition_node);
 
+		// flush conditional to avoid short-circuiting
+		flush_sexp_tree(condition_node);
+
 		// true?
 		if (val == SEXP_TRUE || val == SEXP_KNOWN_TRUE)
 		{
@@ -8790,12 +8792,14 @@
 	{
 		// flush stuff
 		Sexp_applicable_argument_list.clear_nesting_level();
-		flush_sexp_tree(condition_node);
 
 		// evaluate conditional for current argument
 		Sexp_replacement_arguments.push_back(Sexp_nodes[n].text);
 		val = eval_sexp(condition_node);
 
+		// flush conditional to avoid short-circuiting
+		flush_sexp_tree(condition_node);
+
 		// true?
 		if (val == SEXP_TRUE || val == SEXP_KNOWN_TRUE)
 		{

Index: code/parse/sexp.cpp
===================================================================
--- code/parse/sexp.cpp	(revision 10747)
+++ code/parse/sexp.cpp	(working copy)
@@ -8294,7 +8294,7 @@
  */
 int eval_when(int n, int when_op_num)
 {
-	int cond, val, actions;
+	int arg_handler = -1, cond, val, actions;
 	Assert( n >= 0 );
 	arg_item *ptr;
 
@@ -8301,7 +8301,7 @@
 	// get the parts of the sexp and evaluate the conditional
 	if (is_blank_argument_op(when_op_num))
 	{
-		int arg_handler = CAR(n);
+		arg_handler = CAR(n);
 		cond = CADR(n);
 		actions = CDDR(n);
 
@@ -8393,7 +8393,10 @@
 		Sexp_current_argument_nesting_level--;
 	}
 
-	if (Sexp_nodes[cond].value == SEXP_KNOWN_FALSE)
+	// thanks to MageKing17, we need to short-circuit on the correct node!
+	int short_circuit_node = (arg_handler >= 0) ? arg_handler : cond;
+
+	if (Sexp_nodes[short_circuit_node].value == SEXP_KNOWN_FALSE)
 		return SEXP_KNOWN_FALSE;  // no need to waste time on this anymore
 
 	if (val == SEXP_KNOWN_FALSE)