diff --git a/MODULE.bazel b/MODULE.bazel
index b6a5bf124..374f14988 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -52,8 +52,8 @@ maven.install(
     artifacts = [
         "com.google.code.findbugs:jsr305:3.0.2",
         "junit:junit:4.13-beta-3",
-        "com.google.protobuf:protobuf-java:3.6.0",
-        "com.google.protobuf:protobuf-java-util:3.6.0",
+        "com.google.protobuf:protobuf-java:3.25.6",
+        "com.google.protobuf:protobuf-java-util:3.26.6",
         "com.google.guava:guava:27.1-jre",
         "com.google.truth:truth:0.45",
         "com.google.auto.service:auto-service:1.1.1",
diff --git a/src/main/kotlin/io/bazel/kotlin/builder/toolchain/CompilationTaskContext.kt b/src/main/kotlin/io/bazel/kotlin/builder/toolchain/CompilationTaskContext.kt
index 3676806da..c9da0190b 100644
--- a/src/main/kotlin/io/bazel/kotlin/builder/toolchain/CompilationTaskContext.kt
+++ b/src/main/kotlin/io/bazel/kotlin/builder/toolchain/CompilationTaskContext.kt
@@ -93,7 +93,7 @@ class CompilationTaskContext(
     header: String,
     msg: MessageOrBuilder,
   ) {
-    printLines(header, TextFormat.printToString(msg).split("\n"), filterEmpty = true)
+    printLines(header, TextFormat.printer().printToString(msg).split("\n"), filterEmpty = true)
   }
 
   /**
diff --git a/src/main/kotlin/io/bazel/kotlin/builder/toolchain/KotlinToolchain.kt b/src/main/kotlin/io/bazel/kotlin/builder/toolchain/KotlinToolchain.kt
index 776770584..340fbac18 100644
--- a/src/main/kotlin/io/bazel/kotlin/builder/toolchain/KotlinToolchain.kt
+++ b/src/main/kotlin/io/bazel/kotlin/builder/toolchain/KotlinToolchain.kt
@@ -234,8 +234,10 @@ class KotlinToolchain private constructor(
         },
         Preloader.DEFAULT_CLASS_NUMBER_ESTIMATE,
         classLoader,
-        null,
-      )
+      ) { className ->
+        // Preload guava to avoid weird isolation issues.
+        className.startsWith("com.google.common.")
+      }
     }.onFailure {
       throw RuntimeException("$javaHome, $baseJars", it)
     }.getOrThrow()