diff --git a/CHANGELOG.md b/CHANGELOG.md
index f6c7a2b4..5eee8030 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -43,6 +43,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Fixed
 
+- Fix undefined local variable in `CalcFunction::parse()` (#593)
 - Fix PHP notice caused by parsing invalid color values having less than 6 characters (#485)
 - Fix (regression) failure to parse at-rules with strict parsing (#456)
 
diff --git a/config/phpstan-baseline.neon b/config/phpstan-baseline.neon
index 243e36c4..82fcb3f4 100644
--- a/config/phpstan-baseline.neon
+++ b/config/phpstan-baseline.neon
@@ -10,8 +10,3 @@ parameters:
 			count: 2
 			path: ../src/RuleSet/DeclarationBlock.php
 
-		-
-			message: "#^Variable \\$oVal might not be defined\\.$#"
-			count: 1
-			path: ../src/Value/CalcFunction.php
-
diff --git a/src/Value/CalcFunction.php b/src/Value/CalcFunction.php
index f06d9b7e..d0e7cfb3 100644
--- a/src/Value/CalcFunction.php
+++ b/src/Value/CalcFunction.php
@@ -87,7 +87,7 @@ public static function parse(ParserState $oParserState, $bIgnoreCase = false)
                         sprintf(
                             'Next token was expected to be an operand of type %s. Instead "%s" was found.',
                             implode(', ', $aOperators),
-                            $oVal
+                            $oParserState->peek()
                         ),
                         '',
                         'custom',