diff --git a/projects/plugins/boost/.phan/baseline.php b/projects/plugins/boost/.phan/baseline.php
index b58fae407fd1d..04f317e93cfd3 100644
--- a/projects/plugins/boost/.phan/baseline.php
+++ b/projects/plugins/boost/.phan/baseline.php
@@ -15,7 +15,7 @@
     // PhanTypeMismatchReturnProbablyReal : 10+ occurrences
     // PhanTypeArraySuspicious : 9 occurrences
     // PhanTypeMismatchArgument : 8 occurrences
-    // PhanParamTooMany : 7 occurrences
+    // PhanParamTooMany : 6 occurrences
     // PhanPossiblyUndeclaredVariable : 6 occurrences
     // PhanUndeclaredConstant : 5 occurrences
     // PhanUndeclaredFunction : 4 occurrences
@@ -50,7 +50,6 @@
         'app/data-sync/Performance_History_Entry.php' => ['PhanPluginDuplicateConditionalNullCoalescing', 'PhanTypeArraySuspicious'],
         'app/lib/class-cli.php' => ['PhanPluginDuplicateConditionalNullCoalescing', 'PhanTypeMismatchArgument'],
         'app/lib/critical-css/Critical_CSS_State.php' => ['PhanPluginDuplicateConditionalNullCoalescing', 'PhanTypeArraySuspiciousNullable'],
-        'app/lib/critical-css/Regenerate.php' => ['PhanParamTooMany'],
         'app/lib/critical-css/source-providers/providers/Archive_Provider.php' => ['PhanTypeMismatchReturnProbablyReal'],
         'app/lib/critical-css/source-providers/providers/Post_ID_Provider.php' => ['PhanTypeMismatchReturnProbablyReal'],
         'app/lib/critical-css/source-providers/providers/Provider.php' => ['PhanTypeMismatchArgumentInternal'],
diff --git a/projects/plugins/boost/app/lib/critical-css/Critical_CSS_Invalidator.php b/projects/plugins/boost/app/lib/critical-css/Critical_CSS_Invalidator.php
index 71ce3fd324986..e1013a4ae9d32 100644
--- a/projects/plugins/boost/app/lib/critical-css/Critical_CSS_Invalidator.php
+++ b/projects/plugins/boost/app/lib/critical-css/Critical_CSS_Invalidator.php
@@ -7,7 +7,11 @@
 
 namespace Automattic\Jetpack_Boost\Lib\Critical_CSS;
 
+use Automattic\Jetpack_Boost\Admin\Regenerate_Admin_Notice;
 use Automattic\Jetpack_Boost\Lib\Boost_Health;
+use Automattic\Jetpack_Boost\Lib\Critical_CSS\Source_Providers\Source_Providers;
+use Automattic\Jetpack_Boost\Modules\Modules_Setup;
+use Automattic\Jetpack_Boost\Modules\Optimizations\Cloud_CSS\Cloud_CSS;
 use Automattic\Jetpack_Boost\Modules\Optimizations\Cloud_CSS\Cloud_CSS_Followup;
 
 /**
@@ -21,21 +25,35 @@ class Critical_CSS_Invalidator {
 	 * Register hooks.
 	 */
 	public static function init() {
-		add_action( 'jetpack_boost_deactivate', array( __CLASS__, 'clear_data' ) );
+		add_action( 'jetpack_boost_deactivate', array( __CLASS__, 'reset_data' ) );
 		add_action( 'jetpack_boost_critical_css_environment_changed', array( __CLASS__, 'handle_environment_change' ) );
 		add_filter( 'jetpack_boost_total_problem_count', array( __CLASS__, 'update_boost_problem_count' ) );
 	}
 
 	/**
-	 * Clear Critical CSS data.
+	 * Reset Critical CSS data.
+	 * For Cloud CSS, we need to make sure there are providers in the state,
+	 * otherwise Cloud CSS cannot be stored after it is generated by the cloud.
 	 */
-	public static function clear_data() {
+	public static function reset_data() {
 		$storage = new Critical_CSS_Storage();
 		$storage->clear();
 
 		$state = new Critical_CSS_State();
 		$state->clear();
 
+		if ( self::is_cloud_css() ) {
+			$state->prepare_for_generation( ( new Source_Providers() )->get_provider_sources() );
+			$state->save();
+
+			// Clear the regenerate flag so things are nice and tidy.
+			jetpack_boost_ds_delete( 'critical_css_suggest_regenerate' );
+			// Also clear the admin notice flag, so the notice doesn't show up in case
+			// the user is reverted to free Boost.
+			Regenerate_Admin_Notice::dismiss();
+
+		}
+
 		Cloud_CSS_Followup::unschedule();
 	}
 
@@ -44,7 +62,7 @@ public static function clear_data() {
 	 */
 	public static function handle_environment_change( $is_major_change ) {
 		if ( $is_major_change ) {
-			self::clear_data();
+			self::reset_data();
 
 			do_action( 'jetpack_boost_critical_css_invalidated' );
 		}
@@ -58,4 +76,9 @@ public static function update_boost_problem_count( $count ) {
 
 		return $count;
 	}
+
+	public static function is_cloud_css() {
+		$optimizations = ( new Modules_Setup() )->get_status();
+		return isset( $optimizations[ Cloud_CSS::get_slug() ] ) && $optimizations[ Cloud_CSS::get_slug() ];
+	}
 }
diff --git a/projects/plugins/boost/app/lib/critical-css/Critical_CSS_State.php b/projects/plugins/boost/app/lib/critical-css/Critical_CSS_State.php
index 77337d121c297..07e7c978b5132 100644
--- a/projects/plugins/boost/app/lib/critical-css/Critical_CSS_State.php
+++ b/projects/plugins/boost/app/lib/critical-css/Critical_CSS_State.php
@@ -186,6 +186,19 @@ public function set_pending_providers( $providers ) {
 		return $this;
 	}
 
+	/**
+	 * Add providers to the state, sets their status to pending
+	 * and sets the generation status to pending.
+	 *
+	 * @param array $providers The providers to include in the state and set as pending.
+	 * @return $this
+	 */
+	public function prepare_for_generation( $providers ) {
+		$this->set_pending_providers( $providers );
+		$this->state['status'] = self::GENERATION_STATES['pending'];
+		return $this;
+	}
+
 	/**
 	 * Get fresh state
 	 */
diff --git a/projects/plugins/boost/app/lib/critical-css/Regenerate.php b/projects/plugins/boost/app/lib/critical-css/Regenerate.php
index 9a74b501352b9..6b25fdf434c3c 100644
--- a/projects/plugins/boost/app/lib/critical-css/Regenerate.php
+++ b/projects/plugins/boost/app/lib/critical-css/Regenerate.php
@@ -45,7 +45,7 @@ public function start() {
 
 		// Dismiss admin notices
 		Regenerate_Admin_Notice::dismiss();
-		jetpack_boost_ds_delete( 'critical_css_suggest_regenerate', null );
+		jetpack_boost_ds_delete( 'critical_css_suggest_regenerate' );
 
 		return $data;
 	}
diff --git a/projects/plugins/boost/app/modules/optimizations/cloud-css/Cloud_CSS.php b/projects/plugins/boost/app/modules/optimizations/cloud-css/Cloud_CSS.php
index c16f51b452d99..8664505d583cf 100644
--- a/projects/plugins/boost/app/modules/optimizations/cloud-css/Cloud_CSS.php
+++ b/projects/plugins/boost/app/modules/optimizations/cloud-css/Cloud_CSS.php
@@ -178,7 +178,7 @@ public function handle_critical_css_invalidated() {
 	public function get_existing_sources() {
 		$state = new Critical_CSS_State();
 		$data  = $state->get();
-		if ( isset( $data['providers'] ) ) {
+		if ( ! empty( $data['providers'] ) ) {
 			$providers = $data['providers'];
 		} else {
 			$source_providers = new Source_Providers();
diff --git a/projects/plugins/boost/changelog/fix-cloud-css-not-saved-on-theme-switch b/projects/plugins/boost/changelog/fix-cloud-css-not-saved-on-theme-switch
new file mode 100644
index 0000000000000..b583faf49b911
--- /dev/null
+++ b/projects/plugins/boost/changelog/fix-cloud-css-not-saved-on-theme-switch
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+Cloud CSS: Fixed not properly storing CSS returned from the cloud after a theme switch.