                 case .greaterThanOrEqual:
                     return firstAnchor.constraint(
                         greaterThanOrEqualToSystemSpacingBelow: secondAnchor,
+                        multiplier: multiplier
+                    )
+                @unknown default:
+                    assertionFailure("Unknown relation '\(relation)', falling back to `.equal`.", file: file, line: line)
+                    return firstAnchor.constraint(
+                        equalToSystemSpacingBelow: secondAnchor,
                         multiplier: multiplier
                     )
                 }

                        multiplier: multiplier,
                        constant: constant
                    )
                }
            })
    }

                        multiplier: multiplier,
                        constant: constant
                    )
                @unknown default:
                    assertionFailure("Unknown relation '\(relation)', falling back to `.equal`.", file: file, line: line)
                    return anchor.constraint(
                        equalTo: space,
                        multiplier: multiplier,
                        constant: constant
                    )
                }
            })
    }
