diff --git a/internal/cmd/buildtool/android_test.go b/internal/cmd/buildtool/android_test.go
index e8192eeb6..a053bf3d8 100644
--- a/internal/cmd/buildtool/android_test.go
+++ b/internal/cmd/buildtool/android_test.go
@@ -440,12 +440,12 @@ func TestAndroidBuildCdepsZlib(t *testing.T) {
 		expect: []buildtooltest.ExecExpectations{{
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
@@ -493,12 +493,12 @@ func TestAndroidBuildCdepsZlib(t *testing.T) {
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
@@ -546,12 +546,12 @@ func TestAndroidBuildCdepsZlib(t *testing.T) {
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
@@ -599,12 +599,12 @@ func TestAndroidBuildCdepsZlib(t *testing.T) {
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
diff --git a/internal/cmd/buildtool/cdepszlib.go b/internal/cmd/buildtool/cdepszlib.go
index b18fe624f..b8e01f77f 100644
--- a/internal/cmd/buildtool/cdepszlib.go
+++ b/internal/cmd/buildtool/cdepszlib.go
@@ -25,13 +25,13 @@ func cdepsZlibBuildMain(globalEnv *cBuildEnv, deps buildtoolmodel.Dependencies)
 	defer restore()
 
 	// See https://github.com/Homebrew/homebrew-core/blob/master/Formula/z/zlib.rb
-	cdepsMustFetch("https://zlib.net/zlib-1.3.tar.gz")
+	cdepsMustFetch("https://zlib.net/zlib-1.3.1.tar.gz")
 	deps.VerifySHA256( // must be mockable
-		"ff0ba4c292013dbc27530b3a81e1f9a813cd39de01ca5e0f8bf355702efa593e",
-		"zlib-1.3.tar.gz",
+		"9a93b2b7dfdac77ceba5a558a580e74667dd6fede4585b91eefb60f03b72df23",
+		"zlib-1.3.1.tar.gz",
 	)
-	must.Run(log.Log, "tar", "-xf", "zlib-1.3.tar.gz")
-	_ = deps.MustChdir("zlib-1.3") // must be mockable
+	must.Run(log.Log, "tar", "-xf", "zlib-1.3.1.tar.gz")
+	_ = deps.MustChdir("zlib-1.3.1") // must be mockable
 
 	mydir := filepath.Join(topdir, "CDEPS", "zlib")
 	for _, patch := range cdepsMustListPatches(mydir) {
diff --git a/internal/cmd/buildtool/ios_test.go b/internal/cmd/buildtool/ios_test.go
index 82d928139..1377704d0 100644
--- a/internal/cmd/buildtool/ios_test.go
+++ b/internal/cmd/buildtool/ios_test.go
@@ -140,12 +140,12 @@ func TestIOSBuildCdepsZlib(t *testing.T) {
 		expect: []buildtooltest.ExecExpectations{{
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
@@ -194,12 +194,12 @@ func TestIOSBuildCdepsZlib(t *testing.T) {
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
@@ -248,12 +248,12 @@ func TestIOSBuildCdepsZlib(t *testing.T) {
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
diff --git a/internal/cmd/buildtool/linuxcdeps_test.go b/internal/cmd/buildtool/linuxcdeps_test.go
index 6ae5aca74..e46f5fcd5 100644
--- a/internal/cmd/buildtool/linuxcdeps_test.go
+++ b/internal/cmd/buildtool/linuxcdeps_test.go
@@ -40,12 +40,12 @@ func TestLinuxCdepsBuildMain(t *testing.T) {
 		expect: []buildtooltest.ExecExpectations{{
 			Env: []string{},
 			Argv: []string{
-				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.tar.gz",
+				"curl", "-fsSLO", "https://zlib.net/zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},
 			Argv: []string{
-				"tar", "-xf", "zlib-1.3.tar.gz",
+				"tar", "-xf", "zlib-1.3.1.tar.gz",
 			},
 		}, {
 			Env: []string{},