diff --git a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectFluxTests.java b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectFluxTests.java
index 88a00b88e..0a14055bf 100644
--- a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectFluxTests.java
+++ b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectFluxTests.java
@@ -604,7 +604,7 @@ public class SleuthSpanCreatorAspectFluxTests {
 
 	protected static Long id(Tracer tracer) {
 		if (tracer.currentSpan() == null) {
-			return null;
+			throw new IllegalStateException("Current Span is supposed to have a value!");
 		}
 		return tracer.currentSpan().context().spanId();
 	}
diff --git a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectMonoTests.java b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectMonoTests.java
index cc333ffbb..2b6eee34a 100644
--- a/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectMonoTests.java
+++ b/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/annotation/SleuthSpanCreatorAspectMonoTests.java
@@ -660,7 +660,7 @@ public class SleuthSpanCreatorAspectMonoTests {
 
 	protected static Long id(Tracer tracer) {
 		if (tracer.currentSpan() == null) {
-			return null;
+			throw new IllegalStateException("Current Span is supposed to have a value!");
 		}
 		return tracer.currentSpan().context().spanId();
 	}