diff --git a/docs/appendices/0.22.0-migration-guide.md b/docs/appendices/0.22.0-migration-guide.md
new file mode 100644
index 000000000..4b50f72ef
--- /dev/null
+++ b/docs/appendices/0.22.0-migration-guide.md
@@ -0,0 +1,6 @@
+# 0.22.0 Migration Guide
+
+## Changes
+
+- Underscores are no longer valid characters in app names. Please rename applications before upgrading.
+- Process type names specified in Procfile may no longer use characters not valid in DNS records.
diff --git a/docs/getting-started/upgrading.md b/docs/getting-started/upgrading.md
index 8e4406b8f..1aceb7440 100644
--- a/docs/getting-started/upgrading.md
+++ b/docs/getting-started/upgrading.md
@@ -19,6 +19,7 @@ Docker releases updates periodically to their engine. We recommend reading their
 
 Before upgrading, check the migration guides to get comfortable with new features and prepare your deployment to be upgraded.
 
+- [Upgrading to 0.22](/docs/appendices/0.22.0-migration-guide.md)
 - [Upgrading to 0.21](/docs/appendices/0.21.0-migration-guide.md)
 - [Upgrading to 0.20](/docs/appendices/0.20.0-migration-guide.md)
 - [Upgrading to 0.10](/docs/appendices/0.10.0-migration-guide.md)
diff --git a/plugins/common/common.go b/plugins/common/common.go
index dc1e282dd..36cb8760b 100644
--- a/plugins/common/common.go
+++ b/plugins/common/common.go
@@ -739,7 +739,7 @@ func IsValidAppName(appName string) error {
 		return fmt.Errorf("APP must not be null")
 	}
 
-	r, _ := regexp.Compile("^[a-z0-9][^/:A-Z]*$")
+	r, _ := regexp.Compile("^[a-z0-9][^/:_A-Z]*$")
 	if r.MatchString(appName) {
 		return nil
 	}
@@ -749,7 +749,7 @@ func IsValidAppName(appName string) error {
 		os.RemoveAll(appRoot)
 	}
 
-	return errors.New("App name must begin with lowercase alphanumeric character, and cannot include uppercase characters or colons")
+	return errors.New("App name must begin with lowercase alphanumeric character, and cannot include uppercase characters, colons, or underscores")
 }
 
 // VerifyAppName verifies app name format and app existence"
diff --git a/plugins/common/functions b/plugins/common/functions
index d41697179..8f882de11 100755
--- a/plugins/common/functions
+++ b/plugins/common/functions
@@ -185,13 +185,13 @@ is_valid_app_name() {
   local APP="$1"
   [[ -z "$APP" ]] && dokku_log_fail "APP must not be null"
   if [[ "$APP" =~ ^[a-z].* ]] || [[ "$APP" =~ ^[0-9].* ]]; then
-    if [[ ! $APP =~ [A-Z] ]] && [[ ! $APP =~ [:] ]]; then
+    if [[ ! $APP =~ [A-Z] ]] && [[ ! $APP =~ [:] ]] && [[ ! $APP =~ [_] ]]; then
       return 0
     fi
   fi
 
   [[ -d "$DOKKU_ROOT/$APP" ]] && rm -rf "${DOKKU_ROOT:?}/$APP"
-  dokku_log_fail "App name must begin with lowercase alphanumeric character"
+  dokku_log_fail "App name must begin with lowercase alphanumeric character, and cannot include uppercase characters, colons, or underscores"
 }
 
 verify_app_name() {
diff --git a/plugins/ps/post-extract b/plugins/ps/post-extract
new file mode 100755
index 000000000..ac329ccfd
--- /dev/null
+++ b/plugins/ps/post-extract
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+
+trigger-ps-post-extract() {
+  declare desc="ps post-extract plugin trigger"
+  declare trigger="post-extract"
+  declare APP="$1" TMP_WORK_DIR="$2" REV="$3"
+
+  if [[ ! -f "$TMP_WORK_DIR/Procfile" ]]; then
+    return
+  fi
+
+  pushd "$TMP_WORK_DIR" >/dev/null
+  for process_type in $(procfile-util list); do
+    if echo "$process_type" | grep -vqE '^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$'; then
+      dokku_log_fail "Invalid process type name ($process_type)"
+    fi
+  done
+  popd >/dev/null
+}
+
+trigger-ps-post-extract "$@"
diff --git a/tests/unit/apps_1.bats b/tests/unit/apps_1.bats
index f09753bca..28ababc7b 100644
--- a/tests/unit/apps_1.bats
+++ b/tests/unit/apps_1.bats
@@ -86,6 +86,11 @@ teardown() {
   echo "status: $status"
   assert_failure
 
+  run /bin/bash -c "dokku apps:create test_app"
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+
   run /bin/bash -c "dokku --app $TEST_APP apps:create"
   echo "output: $output"
   echo "status: $status"