diff --git a/kilo.c b/kilo.c
index ba59e67..a8aae1b 100644
--- a/kilo.c
+++ b/kilo.c
@@ -259,18 +259,34 @@ int getWindowSize(int *rows, int *cols)
 
 /*** syntax highlighting ***/
 
+int is_separator(int c)
+{
+	return isspace(c) || c == '\0' || strchr(",.()+-/*=~%<>[];", c) != NULL;
+}
+
 void editorUpdateSyntax(erow *row)
 {
 	row->hl = realloc(row->hl, row->rsize);
 	memset(row->hl, HL_NORMAL, row->rsize);
 
-	int i;
-	for (i = 0; i < row->rsize; i++)
+	int prev_sep = 1;
+
+	int i = 0;
+	while (i < row->rsize)
 	{
-		if (isdigit(row->render[i]))
+		char c = row->render[i];
+		unsigned char prev_hl = (i > 0) ? row->hl[i - 1] : HL_NORMAL;
+
+		if (isdigit(c) && (prev_sep || prev_hl == HL_NUMBER))
 		{
 			row->hl[i] = HL_NUMBER;
+			i++;
+			prev_sep = 0;
+			continue;
 		}
+
+		prev_sep = is_separator(c);
+		i++;
 	}
 }