diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheck.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheck.java
index cf6fcfc3c2..43a6c10223 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheck.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheck.java
@@ -1,5 +1,8 @@
 package tech.picnic.errorprone.bugpatterns;
 
+import static com.google.errorprone.BugPattern.LinkType.NONE;
+import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
+import static com.google.errorprone.BugPattern.StandardTags.LIKELY_ERROR;
 import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.ALL;
 import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
 import static com.google.errorprone.matchers.Matchers.allOf;
@@ -11,6 +14,8 @@
 import static com.google.errorprone.matchers.Matchers.methodHasParameters;
 
 import com.google.auto.service.AutoService;
+import com.google.common.collect.ImmutableCollection;
+import com.google.common.collect.ImmutableMap;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker;
@@ -20,17 +25,17 @@
 import com.sun.source.tree.MethodTree;
 
 /**
- * A {@link BugChecker} which flags {@code @RequestParam} parameters that have an invalid type.
+ * A {@link BugChecker} which flags {@code RequestParam} parameters that have an invalid type.
  *
- * <p>Types considered invalid are {@code ImmutableMap} and subtypes of {@code ImmutableCollection}.
+ * <p>Types considered invalid are {@link ImmutableMap} and subtypes of {@link ImmutableCollection}.
  */
 @AutoService(BugChecker.class)
 @BugPattern(
     name = "RequestParamAnnotationCheck",
     summary = "Make sure all `@RequestParam` method parameters are valid",
-    linkType = BugPattern.LinkType.NONE,
-    severity = BugPattern.SeverityLevel.ERROR,
-    tags = BugPattern.StandardTags.LIKELY_ERROR)
+    linkType = NONE,
+    severity = ERROR,
+    tags = LIKELY_ERROR)
 public final class RequestParamAnnotationCheck extends BugChecker implements MethodTreeMatcher {
   private static final long serialVersionUID = 1L;
   private static final String ANN_PACKAGE_PREFIX = "org.springframework.web.bind.annotation.";
@@ -48,13 +53,13 @@ public final class RequestParamAnnotationCheck extends BugChecker implements Met
                   isType(ANN_PACKAGE_PREFIX + "RequestMapping"))),
           methodHasParameters(
               AT_LEAST_ONE,
-              annotations(AT_LEAST_ONE, anyOf(isType(ANN_PACKAGE_PREFIX + "RequestParam")))));
+              annotations(AT_LEAST_ONE, isType(ANN_PACKAGE_PREFIX + "RequestParam"))));
 
   private static final Matcher<MethodTree> HAS_INVALID_REQUEST_PARAM_TYPE =
       methodHasParameters(
           AT_LEAST_ONE,
           allOf(
-              annotations(ALL, anyOf(isType(ANN_PACKAGE_PREFIX + "RequestParam"))),
+              annotations(ALL, isType(ANN_PACKAGE_PREFIX + "RequestParam")),
               anyOf(
                   isSubtypeOf("com.google.common.collect.ImmutableCollection"),
                   isSameType("com.google.common.collect.ImmutableMap"))));
@@ -64,7 +69,9 @@ public Description matchMethod(MethodTree tree, VisitorState state) {
     return HAS_REQUEST_MAPPING_ANNOTATION.matches(tree, state)
             && HAS_INVALID_REQUEST_PARAM_TYPE.matches(tree, state)
         ? buildDescription(tree)
-            .setMessage("At least one defined Request Parameters has an invalid type.")
+            .setMessage(
+                "At least one defined Request Parameter has an invalid type. "
+                    + "`ImmutableMap`, `ImmutableCollection` and subtypes are not allowed.")
             .build()
         : Description.NO_MATCH;
   }
diff --git a/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheckTest.java b/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheckTest.java
index 86c7303a53..9d85f62327 100644
--- a/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheckTest.java
+++ b/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamAnnotationCheckTest.java
@@ -12,12 +12,12 @@ void identification() {
     compilationTestHelper
         .addSourceLines(
             "A.java",
-            "import java.util.List;",
-            "import java.util.Map;",
-            "import java.util.Set;",
             "import com.google.common.collect.ImmutableList;",
             "import com.google.common.collect.ImmutableMap;",
             "import com.google.common.collect.ImmutableSet;",
+            "import java.util.List;",
+            "import java.util.Map;",
+            "import java.util.Set;",
             "import org.springframework.web.bind.annotation.DeleteMapping;",
             "import org.springframework.web.bind.annotation.GetMapping;",
             "import org.springframework.web.bind.annotation.PostMapping;",
@@ -40,6 +40,8 @@ void identification() {
             "",
             "  // BUG: Diagnostic contains:",
             "  @DeleteMapping A delete(@RequestBody String body, @RequestParam ImmutableMap<String, String> param);",
+            "",
+            "  void negative(ImmutableSet<Integer> set, ImmutableMap<String, String> map);",
             "}")
         .doTest();
   }