diff --git a/src/parser/function.rs b/src/parser/function.rs
index 5dc5e9b..c74cd6f 100644
--- a/src/parser/function.rs
+++ b/src/parser/function.rs
@@ -264,6 +264,14 @@ lazy_static! {
             ValueType::Vector,
             false
         ),
+        // MetricsQL extension.
+        function!(
+            "l2_over_time",
+            vec![ValueType::Matrix],
+            0,
+            ValueType::Vector,
+            false
+        ),
         function!("exp", vec![ValueType::Vector], 0, ValueType::Vector, false),
         function!(
             "first_over_time",
diff --git a/src/parser/parse.rs b/src/parser/parse.rs
index 305f25a..7010a24 100644
--- a/src/parser/parse.rs
+++ b/src/parser/parse.rs
@@ -1369,6 +1369,18 @@ mod tests {
                     )
                 })
             }),
+            ("l2_over_time(some_metric[5m])", {
+                Expr::new_matrix_selector(
+                    Expr::from(VectorSelector::from("some_metric")),
+                    duration::MINUTE_DURATION * 5,
+                )
+                .and_then(|ex| {
+                    Expr::new_call(
+                        get_function("l2_over_time").unwrap(),
+                        FunctionArgs::new_args(ex),
+                    )
+                })
+            }),
             ("round(some_metric)", {
                 let ex = Expr::from(VectorSelector::from("some_metric"));
                 Expr::new_call(get_function("round").unwrap(), FunctionArgs::new_args(ex))