diff --git a/src/io/json.cpp b/src/io/json.cpp
index 29c75ad..7be1620 100644
--- a/src/io/json.cpp
+++ b/src/io/json.cpp
@@ -119,7 +119,7 @@ namespace fc
                   in.get();
                   return token.str();
                default:
-                if( isalnum( c ) )
+                if( isalnum( c ) || c == '_' || c == '-' || c == '.' || c == ':' )
                 {
                   token << c;
                   in.get();