diff --git a/src/State/Hub.php b/src/State/Hub.php
index 79573a2e2..bd51b440b 100644
--- a/src/State/Hub.php
+++ b/src/State/Hub.php
@@ -288,7 +288,7 @@ public function startTransaction(TransactionContext $context, array $customSampl
                         $samplingContext->getParentSampled(),
                         $options->getTracesSampleRate() ?? 0
                     );
-                    $sampleSource = $samplingContext->getParentSampled() ? 'parent:sampling_decision' : 'config:traces_sample_rate';
+                    $sampleSource = $samplingContext->getParentSampled() !== null ? 'parent:sampling_decision' : 'config:traces_sample_rate';
                 }
             }