diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35963f6b..cb1301fd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+## v178 (2023-08-14)
+* Add go1.21.0
+* Use go1.21.0 for go1.21
+
 ## v177 (2023-08-07)
 * Add go1.20.7
 * Add go1.19.12
diff --git a/data.json b/data.json
index 8b58edf7..ee612469 100644
--- a/data.json
+++ b/data.json
@@ -2,6 +2,7 @@
   "Go": {
     "DefaultVersion": "go1.12.17",
     "VersionExpansion": {
+      "go1.21": "go1.21.0",
       "go1.20.0": "go1.20",
       "go1.20": "go1.20.7",
       "go1.19.0": "go1.19",
@@ -131,6 +132,7 @@
       "go1.18.10.linux-amd64.tar.gz",
       "go1.19.12.linux-amd64.tar.gz",
       "go1.20.7.linux-amd64.tar.gz",
+      "go1.21.0.linux-amd64.tar.gz",
       "go1.4.3.linux-amd64.tar.gz",
       "go1.6.4.linux-amd64.tar.gz",
       "go1.7.6.linux-amd64.tar.gz",
diff --git a/files.json b/files.json
index fe858000..28f6b40f 100644
--- a/files.json
+++ b/files.json
@@ -775,6 +775,10 @@
     "SHA": "5a9ebcc65c1cce56e0d2dc616aff4c4cedcfbda8cc6f0288cc08cda3b18dcbf1",
     "URL": "https://dl.google.com/go/go1.20.linux-amd64.tar.gz"
   },
+  "go1.21.0.linux-amd64.tar.gz": {
+    "SHA": "d0398903a16ba2232b389fb31032ddf57cac34efda306a0eebac34f0965a0742",
+    "URL": "https://dl.google.com/go/go1.21.0.linux-amd64.tar.gz"
+  },
   "go1.3.1.linux-amd64.tar.gz": {
     "SHA": "3af011cc19b21c7180f2604fd85fbc4ddde97143",
     "URL": "https://storage.googleapis.com/golang/go1.3.1.linux-amd64.tar.gz"
diff --git a/test/fixtures/mod-basic-go121/Procfile b/test/fixtures/mod-basic-go121/Procfile
new file mode 100644
index 00000000..d958350d
--- /dev/null
+++ b/test/fixtures/mod-basic-go121/Procfile
@@ -0,0 +1 @@
+web: fixture
diff --git a/test/fixtures/mod-basic-go121/go.mod b/test/fixtures/mod-basic-go121/go.mod
new file mode 100644
index 00000000..829ebc73
--- /dev/null
+++ b/test/fixtures/mod-basic-go121/go.mod
@@ -0,0 +1,3 @@
+// +heroku goVersion 1.21
+
+module github.com/heroku/fixture
diff --git a/test/fixtures/mod-basic-go121/main.go b/test/fixtures/mod-basic-go121/main.go
new file mode 100644
index 00000000..d8fa9292
--- /dev/null
+++ b/test/fixtures/mod-basic-go121/main.go
@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("hello")
+}
diff --git a/test/run.sh b/test/run.sh
index a3e8f56c..ef771412 100755
--- a/test/run.sh
+++ b/test/run.sh
@@ -368,6 +368,20 @@ testModBasicGo120() {
   assertInstalledFixtureBinary
 }
 
+testModBasicGo121() {
+  fixture "mod-basic-go121"
+
+  assertDetected
+
+  compile
+  assertModulesBoilerplateCaptured
+  assertCaptured "Installing go1.21"
+  assertGoInstallOnlyFixturePackageCaptured
+
+  assertCapturedSuccess
+  assertInstalledFixtureBinary
+}
+
 testModBasicWithoutProcfile() {
   fixture "mod-basic-wo-procfile"