diff --git a/Cargo.lock b/Cargo.lock
index 56158ad0..002f8862 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,3 +1,5 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
 [[package]]
 name = "adler32"
 version = "1.0.3"
@@ -149,8 +151,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "image"
-version = "0.21.0"
-source = "git+https://github.com/PistonDevelopers/image?rev=41dfbae#41dfbaecfa0e702eaef61e4dba156e9be5b2f70d"
+version = "0.21.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "byteorder 1.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lzw 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -257,7 +259,7 @@ dependencies = [
  "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "cloudflare-zlib 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "crc 1.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "image 0.21.0 (git+https://github.com/PistonDevelopers/image?rev=41dfbae)",
+ "image 0.21.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "miniz_oxide 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -419,7 +421,7 @@ dependencies = [
 "checksum deflate 0.7.19 (registry+https://github.com/rust-lang/crates.io-index)" = "8a6abb26e16e8d419b5c78662aa9f82857c2386a073da266840e474d5055ec86"
 "checksum either 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c67353c641dc847124ea1902d69bd753dee9bb3beff9aa3662ecf86c971d1fac"
 "checksum glob 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "8be18de09a56b60ed0edf84bc9df007e30040691af7acd1c41874faac5895bfb"
-"checksum image 0.21.0 (git+https://github.com/PistonDevelopers/image?rev=41dfbae)" = "<none>"
+"checksum image 0.21.2 (registry+https://github.com/rust-lang/crates.io-index)" = "99198e595d012efccf12abf4abc08da2d97be0b0355a2b08d101347527476ba4"
 "checksum inflate 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)" = "1cdb29978cc5797bd8dcc8e5bf7de604891df2a8dc576973d71a281e916db2ff"
 "checksum itertools 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5b8467d9c1cebe26feb08c640139247fac215782d35371ade9a2136ed6085358"
 "checksum lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bc5729f27f159ddd61f4df6228e827e86643d4d3e7c32183cb30a1c08f604a14"
diff --git a/Cargo.toml b/Cargo.toml
index 7c90196b..5a71b928 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -55,11 +55,7 @@ cloudflare-zlib = "^0.2.2"
 [dependencies.image]
 default-features = false
 features = ["png_codec"]
-#FIXME: Use upstream version when 0.22 is released
-#Contains bugfix for issues 167 and 168
-#version = "^0.21.0"
-git = "https://github.com/PistonDevelopers/image"
-rev = "41dfbae"
+version = "^0.21.2"
 
 [features]
 binary = [
diff --git a/src/lib.rs b/src/lib.rs
index 226bdf86..70ff06ca 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -863,7 +863,8 @@ fn perform_strip(png: &mut PngData, opts: &Options) {
                 *b"cHRM", *b"gAMA", *b"iCCP", *b"sBIT", *b"sRGB", *b"bKGD", *b"hIST", *b"pHYs",
                 *b"sPLT",
             ];
-            for hdr in &PRESERVED_HEADERS {
+            let keys: Vec<[u8; 4]> = raw.aux_headers.keys().cloned().collect();
+            for hdr in &keys {
                 if !PRESERVED_HEADERS.contains(hdr) {
                     raw.aux_headers.remove(hdr);
                 }
diff --git a/tests/files/issue-171.png b/tests/files/issue-171.png
new file mode 100644
index 00000000..bf83f52b
Binary files /dev/null and b/tests/files/issue-171.png differ
diff --git a/tests/regression.rs b/tests/regression.rs
index a8dbe045..1b20edee 100644
--- a/tests/regression.rs
+++ b/tests/regression.rs
@@ -600,6 +600,7 @@ fn issue_159() {
 }
 
 #[test]
+#[cfg(target_pointer_width = "64")]
 fn issue_167() {
     test_it_converts(
         "tests/files/issue-167.png",
@@ -610,3 +611,15 @@ fn issue_167() {
         BitDepth::Eight,
     );
 }
+
+#[test]
+fn issue_171() {
+    test_it_converts(
+        "tests/files/issue-171.png",
+        None,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+    );
+}