diff --git a/Cargo.toml b/Cargo.toml
index 5bdf85ff2..b025ad2b9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,7 @@
 
 name = "url"
 # When updating version, also modify html_root_url in the lib.rs
-version = "1.5.0"
+version = "1.5.1"
 authors = ["The rust-url developers"]
 
 description = "URL library for Rust, based on the WHATWG URL Standard"
diff --git a/src/parser.rs b/src/parser.rs
index 8b019bb48..ead0aa9cc 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -57,6 +57,9 @@ simple_enum_error! {
     Overflow => "URLs more than 4 GB are not supported",
 }
 
+#[cfg(feature = "heapsize")]
+known_heap_size!(0, ParseError);
+
 impl fmt::Display for ParseError {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
         self.description().fmt(fmt)