diff --git a/Tests/CoreRasterTests/Fixtures/JPEGFixtures.swift b/Tests/CoreRasterTests/Fixtures/JPEGFixtures.swift
index d4a5663b..91649589 100644
--- a/Tests/CoreRasterTests/Fixtures/JPEGFixtures.swift
+++ b/Tests/CoreRasterTests/Fixtures/JPEGFixtures.swift
@@ -99,8 +99,11 @@ enum JPEGFixtures {
             let b = (0..<size).map { UInt8(truncatingIfNeeded: v >> (8 * (size - 1 - $0))) }
             return littleEndian ? b.reversed() : b
         }
-        let ifd = n(1, 2) + n(0x0112, 2) + n(3, 2) + n(1, 4) + n(orientation, 2) + [0, 0] + n(0, 4)
-        return segment(0xE1, Array("Exif".utf8) + [0, 0] + Array((littleEndian ? "II" : "MM").utf8) + n(42, 2) + n(8, 4) + ifd)
+        // Built as a list of parts: one long `+` chain times out the macOS type checker.
+        let entry: [[UInt8]] = [n(1, 2), n(0x0112, 2), n(3, 2), n(1, 4), n(orientation, 2), [0, 0], n(0, 4)]
+        let order: [UInt8] = Array((littleEndian ? "II" : "MM").utf8)
+        let body: [[UInt8]] = [Array("Exif".utf8), [0, 0], order, n(42, 2), n(8, 4), Array(entry.joined())]
+        return segment(0xE1, Array(body.joined()))
     }
     static func dqt(_ id: Int, _ table: [Int]) -> [UInt8] { segment(0xDB, [UInt8(id)] + zigzag.map { UInt8(clamping: table[$0]) }) }
     static func dht(_ tableClass: Int, _ id: Int, _ t: Huffman) -> [UInt8] {
diff --git a/Tests/CoreRasterTests/Fixtures/PNGFixtures.swift b/Tests/CoreRasterTests/Fixtures/PNGFixtures.swift
index c9b668d4..d5fe4c12 100644
--- a/Tests/CoreRasterTests/Fixtures/PNGFixtures.swift
+++ b/Tests/CoreRasterTests/Fixtures/PNGFixtures.swift
@@ -104,7 +104,8 @@ enum PNGFixtures {
         let size = (stream.count + idats - 1) / idats
         let parts = stride(from: 0, to: stream.count, by: size).map { chunk("IDAT", Array(stream[$0..<min($0 + size, stream.count)])) }
         let head = chunk("IHDR", ihdr(pixels.first?.count ?? 0, pixels.count, depth: depth, colorType: colorType, interlace: interlaced ? 1 : 0))
-        return Data(signature + head + extra.joined() + parts.joined() + chunk("IEND", []))
+        let bytes: [UInt8] = signature + head + Array(extra.joined()) + Array(parts.joined()) + chunk("IEND", [])
+        return Data(bytes)
     }
 
     /// A `width` x `height` grid whose samples run through every value a depth holds, distinct per channel.