diff --git a/pkg/workflow/known_needs_expressions.go b/pkg/workflow/known_needs_expressions.go
index 068bdc03056..30f26d93184 100644
--- a/pkg/workflow/known_needs_expressions.go
+++ b/pkg/workflow/known_needs_expressions.go
@@ -142,12 +142,11 @@ func filterExpressionsForActivation(mappings []*ExpressionMapping, customJobs ma
 		}
 		// Extract the job name (needs.<jobName>.*)
 		rest := m.Content[len("needs."):]
-		dotIdx := strings.Index(rest, ".")
-		if dotIdx < 0 {
+		jobName, _, ok := strings.Cut(rest, ".")
+		if !ok {
 			filtered = append(filtered, m)
 			continue
 		}
-		jobName := rest[:dotIdx]
 		// If it's a custom job NOT in beforeActivationJobs, drop it
 		if _, isCustomJob := customJobs[jobName]; isCustomJob && !beforeActivationSet[jobName] {
 			knownNeedsLog.Printf("Filtered post-activation expression from activation substitution step: %s", m.Content)