diff --git a/src/settings.h b/src/settings.h
@@ -572,12 +572,15 @@ class Settings
 		return value;
 	}
 
-	u32 getFlagStr(std::string name, FlagDesc *flagdesc)
+	u32 getFlagStr(std::string name, FlagDesc *flagdesc, u32 *flagmask)
 	{
 		std::string val = get(name);
-		return (isdigit(val[0])) ? stoi(val) : readFlagString(val, flagdesc);
+		return (isdigit(val[0])) ? stoi(val) :
+			readFlagString(val, flagdesc, flagmask);
 	}
 
+	// N.B. if getStruct() is used to read a non-POD aggregate type,
+	// the behavior is undefined.
 	bool getStruct(std::string name, std::string format, void *out, size_t olen)
 	{
 		size_t len = olen;
@@ -755,10 +758,19 @@ class Settings
 		}
 	}
 
+	// N.B. getFlagStrNoEx() does not set val, but merely modifies it.  Thus,
+	// val must be initialized before using getFlagStrNoEx().  The intention of
+	// this is to simplify modifying a flags field from a default value.
 	bool getFlagStrNoEx(std::string name, u32 &val, FlagDesc *flagdesc)
 	{
 		try {
-			val = getFlagStr(name, flagdesc);
+			u32 flags, flagmask;
+
+			flags = getFlagStr(name, flagdesc, &flagmask);
+
+			val &= ~flagmask;
+			val |=  flags;
+
 			return true;
 		} catch (SettingNotFoundException &e) {
 			return false;
@@ -856,6 +868,9 @@ class Settings
 	}
 
 	//////////// Set setting
+
+	// N.B. if setStruct() is used to write a non-POD aggregate type,
+	// the behavior is undefined.
 	bool setStruct(std::string name, std::string format, void *value)
 	{
 		char sbuf[2048];
@@ -959,10 +974,11 @@ class Settings
 		set(name, std::string(sbuf));
 		return true;
 	}
-
-	void setFlagStr(std::string name, u32 flags, FlagDesc *flagdesc)
+
+	void setFlagStr(std::string name, u32 flags,
+		FlagDesc *flagdesc, u32 flagmask)
 	{
-		set(name, writeFlagString(flags, flagdesc));
+		set(name, writeFlagString(flags, flagdesc, flagmask));
 	}
 
 	void setBool(std::string name, bool value)

diff --git a/src/util/string.cpp b/src/util/string.cpp
@@ -108,46 +108,63 @@ std::string urldecode(std::string str)
 	return oss.str();
 }
 
-u32 readFlagString(std::string str, FlagDesc *flagdesc) {
-	u32 result = 0;
+u32 readFlagString(std::string str, FlagDesc *flagdesc, u32 *flagmask)
+{
+	u32 result = 0, mask = 0;
 	char *s = &str[0];
 	char *flagstr, *strpos = NULL;
-	
+
 	while ((flagstr = strtok_r(s, ",", &strpos))) {
 		s = NULL;
-		
+
 		while (*flagstr == ' ' || *flagstr == '\t')
 			flagstr++;
-
+
+		bool flagset = true;
+		if (!strncasecmp(flagstr, "no", 2)) {
+			flagset = false;
+			flagstr += 2;
+		}
+
 		for (int i = 0; flagdesc[i].name; i++) {
 			if (!strcasecmp(flagstr, flagdesc[i].name)) {
-				result |= flagdesc[i].flag;
+				mask |= flagdesc[i].flag;
+				if (flagset)
+					result |= flagdesc[i].flag;
 				break;
 			}
 		}
 	}
-
+
+	if (flagmask)
+		*flagmask = mask;
+
 	return result;
 }
 
-std::string writeFlagString(u32 flags, FlagDesc *flagdesc) {
+std::string writeFlagString(u32 flags, FlagDesc *flagdesc, u32 flagmask)
+{
 	std::string result;
-	
+
 	for (int i = 0; flagdesc[i].name; i++) {
-		if (flags & flagdesc[i].flag) {
+		if (flagmask & flagdesc[i].flag) {
+			if (!(flags & flagdesc[i].flag))
+				result += "no";
+
 			result += flagdesc[i].name;
 			result += ", ";
 		}
 	}
-	
+
 	size_t len = result.length();
 	if (len >= 2)
 		result.erase(len - 2, 2);
-	
+
 	return result;
 }
 
-char *mystrtok_r(char *s, const char *sep, char **lasts) {
+char *mystrtok_r(char *s, const char *sep, char **lasts)
+{
 	char *t;
 
 	if (!s)
@@ -172,7 +189,8 @@ char *mystrtok_r(char *s, const char *sep, char **lasts) {
 	return s;
 }
 
-u64 read_seed(const char *str) {
+u64 read_seed(const char *str)
+{
 	char *endptr;
 	u64 num;
 

diff --git a/src/util/string.h b/src/util/string.h
@@ -319,8 +319,8 @@ inline std::string unescape_string(std::string &s)
 std::string translatePassword(std::string playername, std::wstring password);
 std::string urlencode(std::string str);
 std::string urldecode(std::string str);
-u32 readFlagString(std::string str, FlagDesc *flagdesc);
-std::string writeFlagString(u32 flags, FlagDesc *flagdesc);
+u32 readFlagString(std::string str, FlagDesc *flagdesc, u32 *flagmask);
+std::string writeFlagString(u32 flags, FlagDesc *flagdesc, u32 flagmask);
 char *mystrtok_r(char *s, const char *sep, char **lasts);
 u64 read_seed(const char *str);