diff --git a/json.zig b/json.zig
index 7d426e1e21b0bfc643554fd2ce67bea95c88a2a4..3b139d6bb72169a4e42001edadd68f8a32179ae9 100644
--- a/json.zig
+++ b/json.zig
@@ -207,6 +207,7 @@ fn parseNumber(alloc: std.mem.Allocator, p: *Parser) anyerror!?ValueIndex {
         }
         if (characters.items.len == l) return error.JsonExpectedTODO;
     }
+    if (characters.items.len == 1 and characters.items[0] == '-') return error.JsonExpectedTODO;
 
     return try p.addNumber(alloc, characters.items);
 }