diff --git a/prometheus/histogram_test.go b/prometheus/histogram_test.go
index f3ee917..1a19df2 100644
--- a/prometheus/histogram_test.go
+++ b/prometheus/histogram_test.go
@@ -382,6 +382,7 @@ func TestHistogramAtomicObserve(t *testing.T) {
 				return
 			default:
 				his.Observe(1)
+				time.Sleep(time.Nanosecond)
 			}
 		}
 	}