diff --git a/gtk/gtkcssprovider.c b/gtk/gtkcssprovider.c
index 2de3a8ac7a..a0be44ab9f 100644
--- a/gtk/gtkcssprovider.c
+++ b/gtk/gtkcssprovider.c
@@ -1982,7 +1982,7 @@ symbolic_color_parse_str (const gchar  *string,
       str++;
       end = str;
 
-      while (*end == '-' || *end == '_' || g_ascii_isalpha (*end))
+      while (*end == '-' || *end == '_' || g_ascii_isalnum (*end))
         end++;
 
       name = g_strndup (str, end - str);