diff --git a/linkerd/addr/src/lib.rs b/linkerd/addr/src/lib.rs
index 733d65f5d4..45d2e49dc9 100644
--- a/linkerd/addr/src/lib.rs
+++ b/linkerd/addr/src/lib.rs
@@ -82,11 +82,26 @@ impl Addr {
         match self {
             Addr::Name(n) => n.as_http_authority(),
             Addr::Socket(ref a) if a.port() == 80 => {
-                http::uri::Authority::from_str(&a.ip().to_string())
-                    .expect("SocketAddr must be valid authority")
+                let ip = if a.is_ipv4() {
+                    a.ip().to_string()
+                } else {
+                    // When IPv6 or later addresses are used in an authority,
+                    // they must be within square brackets. See
+                    // https://tools.ietf.org/html/rfc3986#section-3.2 for
+                    // details. The `fmt::Display` implementation of the
+                    // `Ipv6Addr` type does not include brackets, so we must add
+                    // them ourselves.
+                    format!("[{}]", a.ip())
+                };
+                http::uri::Authority::from_str(&ip).unwrap_or_else(|err| {
+                    panic!("SocketAddr ({}) must be valid authority: {}", a, err)
+                })
+            }
+            Addr::Socket(a) => {
+                http::uri::Authority::from_str(&a.to_string()).unwrap_or_else(|err| {
+                    panic!("SocketAddr ({}) must be valid authority: {}", a, err)
+                })
             }
-            Addr::Socket(a) => http::uri::Authority::from_str(&a.to_string())
-                .expect("SocketAddr must be valid authority"),
         }
     }
 
@@ -257,6 +272,65 @@ mod tests {
             assert_eq!(a.is_loopback(), *expected_result, "{:?}", host)
         }
     }
+
+    fn test_to_http_authority(cases: &[&str]) {
+        let width = cases.iter().map(|s| s.len()).max().unwrap_or(0);
+        for host in cases {
+            print!("trying {:1$} ... ", host, width);
+            Addr::from_str(host).unwrap().to_http_authority();
+            println!("ok");
+        }
+    }
+
+    #[test]
+    fn to_http_authority_names_port_80() {
+        test_to_http_authority(&[
+            "localhost:80",
+            "localhost.:80",
+            "LocalhOsT.:80",
+            "mlocalhost.:80",
+            "localhost1.:80",
+        ])
+    }
+
+    #[test]
+    fn to_http_authority_names() {
+        test_to_http_authority(&[
+            "localhost:9090",
+            "localhost.:9090",
+            "LocalhOsT.:9090",
+            "mlocalhost.:9090",
+            "localhost1.:9090",
+        ])
+    }
+
+    #[test]
+    fn to_http_authority_ipv4_port_80() {
+        test_to_http_authority(&["10.7.0.42:80", "127.0.0.1:80"])
+    }
+
+    #[test]
+    fn to_http_authority_ipv4() {
+        test_to_http_authority(&["10.7.0.42:9090", "127.0.0.1:9090"])
+    }
+
+    #[test]
+    fn to_http_authority_ipv6_port_80() {
+        test_to_http_authority(&[
+            "[2001:0db8:0000:0000:0000:8a2e:0370:7334]:80",
+            "[2001:db8::8a2e:370:7334]:80",
+            "[::1]:80",
+        ])
+    }
+
+    #[test]
+    fn to_http_authority_ipv6() {
+        test_to_http_authority(&[
+            "[2001:0db8:0000:0000:0000:8a2e:0370:7334]:9090",
+            "[2001:db8::8a2e:370:7334]:9090",
+            "[::1]:9090",
+        ])
+    }
 }
 
 #[cfg(fuzzing)]