diff --git a/src/string.cpp b/src/string.cpp
index 644c9d3c18..e850c4b7e1 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -480,9 +480,9 @@ bool IsValidChar(WChar key, CharSetFilter afilter)
 		case CS_ALPHANUMERAL:  return IsPrintable(key);
 		case CS_NUMERAL:       return (key >= '0' && key <= '9');
 #if !defined(STRGEN) && !defined(SETTINGSGEN)
-		case CS_NUMERAL_DECIMAL: return (key >= '0' && key <= '9') || key == '.' || key == GetDecimalSeparatorChar();
+		case CS_NUMERAL_DECIMAL: return (key >= '0' && key <= '9') || key == '.' || key == '-' || key == GetDecimalSeparatorChar();
 #else
-		case CS_NUMERAL_DECIMAL: return (key >= '0' && key <= '9') || key == '.';
+		case CS_NUMERAL_DECIMAL: return (key >= '0' && key <= '9') || key == '.' || key == '-';
 #endif
 		case CS_NUMERAL_SPACE: return (key >= '0' && key <= '9') || key == ' ';
 		case CS_ALPHA:         return IsPrintable(key) && !(key >= '0' && key <= '9');
diff --git a/src/string_type.h b/src/string_type.h
index cca9af6e4a..1e01631a0a 100644
--- a/src/string_type.h
+++ b/src/string_type.h
@@ -26,7 +26,7 @@
 enum CharSetFilter {
 	CS_ALPHANUMERAL,      ///< Both numeric and alphabetic and spaces and stuff
 	CS_NUMERAL,           ///< Only numeric ones
-	CS_NUMERAL_DECIMAL,   ///< Only numeric and decimal separaters
+	CS_NUMERAL_DECIMAL,   ///< Only numeric, decimal separaters, and minus/negative
 	CS_NUMERAL_SPACE,     ///< Only numbers and spaces
 	CS_ALPHA,             ///< Only alphabetic values
 	CS_HEXADECIMAL,       ///< Only hexadecimal characters