diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java
index 2b36c5ee9de..9b20ea23cb3 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java
@@ -1328,11 +1328,13 @@ StepVerifier.Step<T> after(StepVerifier.Step<T> step, T object) {
     }
   }
 
-  /** Avoid value collection when verifying that a {@link Flux} emits exactly one value. */
-  static final class FluxAsStepVerifierExpectNext<T> {
+  /** Avoid list collection when verifying that a {@link Flux} emits exactly one value. */
+  // XXX: This rule assumes that the matched collector does not drop elements. Consider introducing
+  // a `@Matches(DoesNotDropElements.class)` or `@NotMatches(MayDropElements.class)` guard.
+  static final class FluxAsStepVerifierExpectNext<T, L extends List<T>> {
     @BeforeTemplate
-    StepVerifier.Step<ImmutableList<T>> before(Flux<T> flux, T object) {
-      return flux.collect(toImmutableList())
+    StepVerifier.Step<L> before(Flux<T> flux, Collector<? super T, ?, L> listCollector, T object) {
+      return flux.collect(listCollector)
           .as(StepVerifier::create)
           .assertNext(list -> assertThat(list).containsExactly(object));
     }
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
index 07bfd9d45d8..4bb35ca921e 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestInput.java
@@ -422,12 +422,16 @@ ImmutableSet<StepVerifier.Step<String>> testStepVerifierStepExpectNext() {
         StepVerifier.create(Mono.just("baz")).expectNextMatches("qux"::equals));
   }
 
-  Duration testFluxAsStepVerifierExpectNext() {
-    return Flux.just(1)
-        .collect(toImmutableList())
-        .as(StepVerifier::create)
-        .assertNext(list -> assertThat(list).containsExactly(2))
-        .verifyComplete();
+  ImmutableSet<StepVerifier.Step<?>> testFluxAsStepVerifierExpectNext() {
+    return ImmutableSet.of(
+        Flux.just(1)
+            .collect(toImmutableList())
+            .as(StepVerifier::create)
+            .assertNext(list -> assertThat(list).containsExactly(2)),
+        Flux.just(3)
+            .collect(toCollection(ArrayList::new))
+            .as(StepVerifier::create)
+            .assertNext(list -> assertThat(list).containsExactly(4)));
   }
 
   Duration testStepVerifierLastStepVerifyComplete() {
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
index 7d6cb098983..099daa1bd6a 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ReactorRulesTestOutput.java
@@ -413,8 +413,10 @@ ImmutableSet<StepVerifier.Step<String>> testStepVerifierStepExpectNext() {
         StepVerifier.create(Mono.just("baz")).expectNext("qux"));
   }
 
-  Duration testFluxAsStepVerifierExpectNext() {
-    return Flux.just(1).as(StepVerifier::create).expectNext(2).verifyComplete();
+  ImmutableSet<StepVerifier.Step<?>> testFluxAsStepVerifierExpectNext() {
+    return ImmutableSet.of(
+        Flux.just(1).as(StepVerifier::create).expectNext(2),
+        Flux.just(3).as(StepVerifier::create).expectNext(4));
   }
 
   Duration testStepVerifierLastStepVerifyComplete() {