Index: code/mission/missionbriefcommon.cpp
===================================================================
--- code/mission/missionbriefcommon.cpp	(revision 10985)
+++ code/mission/missionbriefcommon.cpp	(working copy)
@@ -1425,7 +1425,7 @@
  */
 bool is_a_word_separator(char character)
 {
-	return character <= 32;					//  all control characters including space, newline, and tab
+	return ((character >= 0) && (character <= 32)); // all control characters including space, newline, and tab
 }
 
 /**