diff --git a/src/slash.c b/src/slash.c
index d68f028..fbb581f 100644
--- a/src/slash.c
+++ b/src/slash.c
@@ -403,8 +403,67 @@ __attribute__((weak)) int slash_prompt(struct slash *slash) {
 
 slash_process_cmd_line_hook_t slash_process_cmd_line_hook  = NULL;
 
-int slash_execute(struct slash *slash, char *line)
+static const int minus_unicode_bytes[] = { 0xE2, 0x88, 0x92 };
+
+static bool has_bad_unicode (struct slash *slash, unsigned char *c, bool in_quotes, int *mightbeminus) {
+	/* Check for non-ASCII characters outside quotes */
+	if ((*c & 0x80) != 0 && !in_quotes) {
+		if (*c == minus_unicode_bytes[*mightbeminus]) {
+			*mightbeminus = *mightbeminus + 1;
+			if (*mightbeminus == sizeof(minus_unicode_bytes)/sizeof(minus_unicode_bytes[0])) {
+				/* Yep, it's a minus sign */
+				*c = '-';
+				memmove(c-2, c, strlen(c)+1);
+				*mightbeminus = 0;
+			}
+			return false;
+		} else {
+			*mightbeminus = 0;
+			printf(" Got non-ascii character 0x%02x outside of quotes, ignoring line\n", *c&0xFF);
+			return true;
+		}
+	} else {
+		*mightbeminus = 0;
+	}
+	return false;
+}
+
+static bool in_quote(unsigned char c, bool quote[3]) {
+	if (c == '\"' && !quote[0]) quote[1] = !quote[1];
+	else if (c == '\'' && !quote[1]) quote[0] = !quote[0];
+	else if (c == '#' && !quote[0] && !quote[1]) quote[2] = true;
+	return quote[0] || quote[1] || quote[2];
+}
+
+static bool has_unicode(struct slash *slash, char *line) {
+	bool result = false;
+	bool quote[3] = { false, false, false }; /* Index 0 represents double quote, index 1 represents single quote, index 2 represents a comment */
+	int mightbeminus = 0;
+	for (unsigned char *c = (unsigned char *)line; *c != '\0'; c++) {
+		if(has_bad_unicode(slash, c, in_quote(*c, quote), &mightbeminus)) {
+			result = true;
+			break;
+		}
+	}
+	return result;
+}
+
+static void strip_comment(char *line) {
+	bool quote[3] = { false, false, false }; /* Index 0 represents double quote, index 1 represents single quote, index 2 represents a comment */
+	for (int i = 1; line[i] != '\0'; i++) {
+		if(!in_quote(line[i-1], quote) && line[i] == '#') {
+			line[i] = '\0';
+			return;
+		}
+	}
+}
+
+int slash_execute(struct slash *slash, char *org_line)
 {
+	char *line = org_line;
+	if (has_unicode(slash, line)) {
+		return EINVAL;
+	}
 	struct slash_command *command;
 	char *args, *argv[SLASH_ARG_MAX];
 	char *processed_cmd_line = NULL, *line_to_use;
@@ -417,6 +476,10 @@ int slash_execute(struct slash *slash, char *line)
 	if (line[0] == '#') {
 		return SLASH_SUCCESS;
 	}
+	/* Skip heading white spaces */
+	while (*line && isspace((unsigned int) *line))
+		line++;
+	strip_comment(line);
 
 	if(NULL != slash_process_cmd_line_hook) {
 		processed_cmd_line = slash_process_cmd_line_hook(line);
@@ -870,6 +933,8 @@ char *slash_readline(struct slash *slash)
 	char *ret = slash->buffer;
 	int c, esc[3];
 	bool done = false, escaped = false;
+	bool quote[3] = { false, false, false }; /* Index 0 represents double quote, index 1 represents single quote, index 2 represents a comment */
+	int mightbeminus = 0;
 
 	/* Reset buffer */
 	slash_reset(slash);
@@ -999,9 +1064,35 @@ char *slash_readline(struct slash *slash)
 				/* Unknown control */
 				break;
 			}
-		} else if (isprint(c)) {
-			/* Add to buffer */
-			slash_insert(slash, c);
+		} else {
+			/* Check for non-ASCII characters outside quotes */
+			if (c == minus_unicode_bytes[mightbeminus]) {
+				mightbeminus++;
+				if (mightbeminus == sizeof(minus_unicode_bytes)/sizeof(minus_unicode_bytes[0])) {
+					slash_insert(slash, '-');
+					slash_refresh(slash, 0);
+					mightbeminus = 0;
+				}
+				continue;
+			}
+			if (!in_quote((unsigned char)c, quote) && (c & 0x80) != 0) {
+				printf(" Got non-ascii character 0x%02x outside of quotes, ignoring line\n", c&0xFF);
+
+				/* Discard the rest of the line */
+				do { c = slash_getchar(slash); } 
+				while (c != '\n' && c != '\r' && c >= 0);
+
+				slash_reset(slash);
+				done = true;
+				break;
+			}
+			mightbeminus = 0;
+
+			/* If inside a quote, unrecognised characters are ignored */
+			if (isprint(c)) {
+				/* Add to buffer */
+				slash_insert(slash, c);
+			}
 		}
 
 		slash->last_char = c;