diff --git a/src/Parsing/ParserState.php b/src/Parsing/ParserState.php
index 06b083e6..19d1a545 100644
--- a/src/Parsing/ParserState.php
+++ b/src/Parsing/ParserState.php
@@ -231,7 +231,7 @@ public function parseCharacter($bIsForIdentifier)
      * @throws UnexpectedEOFException
      * @throws UnexpectedTokenException
      */
-    public function consumeWhiteSpace()
+    public function consumeWhiteSpace(): array
     {
         $aComments = [];
         do {
diff --git a/src/Property/CSSNamespace.php b/src/Property/CSSNamespace.php
index 0d7eb496..ad87a7d8 100644
--- a/src/Property/CSSNamespace.php
+++ b/src/Property/CSSNamespace.php
@@ -115,7 +115,7 @@ public function atRuleName()
     /**
      * @return array<int, string>
      */
-    public function atRuleArgs()
+    public function atRuleArgs(): array
     {
         $aResult = [$this->mUrl];
         if ($this->sPrefix) {
diff --git a/src/Property/Import.php b/src/Property/Import.php
index d715a7a0..f956afb4 100644
--- a/src/Property/Import.php
+++ b/src/Property/Import.php
@@ -98,7 +98,7 @@ public function atRuleName()
     /**
      * @return array<int, URL|string>
      */
-    public function atRuleArgs()
+    public function atRuleArgs(): array
     {
         $aResult = [$this->oLocation];
         if ($this->sMediaQuery) {
diff --git a/src/Rule/Rule.php b/src/Rule/Rule.php
index fc00c880..2c56f7de 100644
--- a/src/Rule/Rule.php
+++ b/src/Rule/Rule.php
@@ -238,7 +238,7 @@ public function setValues(array $aSpaceSeparatedValues)
      *             Old-Style 2-dimensional array returned. Retained for (some) backwards-compatibility.
      *             Use `getValue()` instead and check for the existence of a (nested set of) ValueList object(s).
      */
-    public function getValues()
+    public function getValues(): array
     {
         if (!$this->mValue instanceof RuleValueList) {
             return [[$this->mValue]];