diff --git a/phpstan.neon b/phpstan.neon
index d73aeaf8..3aeae931 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -12,10 +12,3 @@ parameters:
         -
             path: %rootDir%/../../../src/GetPostDynamicFunctionReturnTypeExtension.php
             message: "#^Strict comparison using !== between PhpParser\\\\Node\\\\Expr and 'OBJECT' will always evaluate to true\\.$#"
-        # Accessing value of function arguments.
-        -
-            message: "#^Cannot access offset 'fields' on PHPStan\\\\Type\\\\Constant\\\\ConstantArrayType\\.$#"
-            path: src/GetPostsDynamicFunctionReturnTypeExtension.php
-        -
-            message: "#^Parameter \\#1 \\$encoded_string of function parse_str expects string, PHPStan\\\\Type\\\\Constant\\\\ConstantStringType given\\.$#"
-            path: src/GetPostsDynamicFunctionReturnTypeExtension.php
diff --git a/src/GetPostsDynamicFunctionReturnTypeExtension.php b/src/GetPostsDynamicFunctionReturnTypeExtension.php
index 74c6800f..1f01bd4b 100644
--- a/src/GetPostsDynamicFunctionReturnTypeExtension.php
+++ b/src/GetPostsDynamicFunctionReturnTypeExtension.php
@@ -42,11 +42,21 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 
 		// Called with an array argument
 		if ($argumentType instanceof ConstantArrayType) {
-			$fields = $argumentType['fields'] ?? 'all';
+			foreach($argumentType->getKeyTypes() as $index => $key) {
+				if (! $key instanceof ConstantStringType || $key->getValue() !== 'fields') {
+					continue;
+				}
+
+				$fieldsType = $argumentType->getValueTypes()[$index];
+				if ($fieldsType instanceof ConstantStringType) {
+					$fields = $fieldsType->getValue();
+				}
+				break;
+			}
 		}
 		// Called with a string argument
 		if ($argumentType instanceof ConstantStringType) {
-			parse_str($argumentType, $variables);
+			parse_str($argumentType->getValue(), $variables);
 			$fields = $variables['fields'] ?? 'all';
 		}