diff --git a/java/core/BUILD b/java/core/BUILD
index 20bf589..aa7ba62 100644
--- a/java/core/BUILD
+++ b/java/core/BUILD
@@ -239,6 +239,7 @@
         "conformance_test",
         "core_build_test",
         "core_tests",
+        "utf8_tests",
     ],
 )
 
@@ -258,10 +259,12 @@
 
 junit_tests(
     name = "core_tests",
-    size = "large",
+    size = "small",
     srcs = glob(
         ["src/test/java/**/*.java"],
         exclude = [
+            "src/test/java/com/google/protobuf/DecodeUtf8Test.java",
+            "src/test/java/com/google/protobuf/IsValidUtf8Test.java",
             "src/test/java/com/google/protobuf/TestUtil.java",
             "src/test/java/com/google/protobuf/TestUtilLite.java",
         ],
@@ -279,6 +282,24 @@
     ],
 )
 
+# The UTF-8 validation tests are much slower than the other tests, so they get
+# their own test target with a longer timeout.
+junit_tests(
+    name = "utf8_tests",
+    size = "large",
+    srcs = [
+        "src/test/java/com/google/protobuf/DecodeUtf8Test.java",
+        "src/test/java/com/google/protobuf/IsValidUtf8Test.java",
+        "src/test/java/com/google/protobuf/IsValidUtf8TestUtil.java",
+    ],
+    deps = [
+        ":core",
+        "@maven//:com_google_guava_guava",
+        "@maven//:com_google_truth_truth",
+        "@maven//:junit_junit",
+    ],
+)
+
 java_lite_proto_library(
     name = "generic_test_protos_java_proto_lite",
     visibility = [
@@ -361,6 +382,7 @@
     "src/test/java/com/google/protobuf/TypeRegistryTest.java",
     "src/test/java/com/google/protobuf/UnknownEnumValueTest.java",
     "src/test/java/com/google/protobuf/UnknownFieldSetLiteTest.java",
+    "src/test/java/com/google/protobuf/UnknownFieldSetPerformanceTest.java",
     "src/test/java/com/google/protobuf/UnknownFieldSetTest.java",
     "src/test/java/com/google/protobuf/WellKnownTypesTest.java",
     "src/test/java/com/google/protobuf/WireFormatTest.java",