diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamType.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamType.java
index eada0abe492..c74ca1f329d 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamType.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/RequestParamType.java
@@ -77,8 +77,8 @@ private static ImmutableList<String> includedClassNames(ErrorProneFlags flags) {
   private static ImmutableList<Matcher<Tree>> getSupportedClasses(
       ImmutableList<String> inclusions) {
     return inclusions.stream()
-        .filter(inclusion -> !inclusion.isEmpty())
         .map(String::trim)
+        .filter(inclusion -> !inclusion.isEmpty())
         .map(inclusion -> isSubtypeOf(createClass(inclusion)))
         .collect(toImmutableList());
   }
diff --git a/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamTypeTest.java b/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamTypeTest.java
index cb268714985..e024be4dc01 100644
--- a/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamTypeTest.java
+++ b/error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/RequestParamTypeTest.java
@@ -17,6 +17,9 @@ final class RequestParamTypeTest {
           .setArgs(
               ImmutableList.of(
                   "-XepOpt:RequestParamType:Includes=com.google.common.collect.ImmutableSet"));
+  private final CompilationTestHelper restrictedWithInvalidFlagCompilationTestHelper =
+      CompilationTestHelper.newInstance(RequestParamType.class, getClass())
+          .setArgs(ImmutableList.of("-XepOpt:RequestParamType:Includes="));
 
   @Test
   void identification() {
@@ -167,4 +170,61 @@ void identificationOfIncludedSubClass() {
             "}")
         .doTest();
   }
+
+  @Test
+  void identificationOfInvalidFlag() {
+    restrictedWithInvalidFlagCompilationTestHelper
+        .addSourceLines(
+            "A.java",
+            "import com.google.common.collect.ImmutableBiMap;",
+            "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.jspecify.annotations.Nullable;",
+            "import org.springframework.web.bind.annotation.DeleteMapping;",
+            "import org.springframework.web.bind.annotation.GetMapping;",
+            "import org.springframework.web.bind.annotation.PostMapping;",
+            "import org.springframework.web.bind.annotation.PutMapping;",
+            "import org.springframework.web.bind.annotation.RequestBody;",
+            "import org.springframework.web.bind.annotation.RequestParam;",
+            "",
+            "interface A {",
+            "  @PostMapping",
+            "  A properRequestParam(@RequestBody String body);",
+            "",
+            "  @GetMapping",
+            "  A properRequestParam(@RequestParam int param);",
+            "",
+            "  @GetMapping",
+            "  A properRequestParam(@RequestParam List<String> param);",
+            "",
+            "  @PostMapping",
+            "  A properRequestParam(@RequestBody String body, @RequestParam Set<String> param);",
+            "",
+            "  @PutMapping",
+            "  A properRequestParam(@RequestBody String body, @RequestParam Map<String, String> param);",
+            "",
+            "  @GetMapping",
+            "  // BUG: Diagnostic contains:",
+            "  A get(@RequestParam ImmutableBiMap<String, String> param);",
+            "",
+            "  @PostMapping",
+            "  // BUG: Diagnostic contains:",
+            "  A post(@Nullable @RequestParam ImmutableList<String> param);",
+            "",
+            "  @PutMapping",
+            "  // BUG: Diagnostic contains:",
+            "  A put(@RequestBody String body, @RequestParam ImmutableSet<String> param);",
+            "",
+            "  @DeleteMapping",
+            "  // BUG: Diagnostic contains:",
+            "  A delete(@RequestBody String body, @RequestParam ImmutableMap<String, String> param);",
+            "",
+            "  void negative(ImmutableSet<Integer> set, ImmutableMap<String, String> map);",
+            "}")
+        .doTest();
+  }
 }