diff --git a/core/src/main/java/com/google/common/truth/Platform.java b/core/src/main/java/com/google/common/truth/Platform.java
index c6a2f76d9..d24da88b5 100644
--- a/core/src/main/java/com/google/common/truth/Platform.java
+++ b/core/src/main/java/com/google/common/truth/Platform.java
@@ -362,4 +362,11 @@ static boolean kotlinRangeContains(Iterable<?> haystack, @Nullable Object needle
               throw newLinkageError(e);
             }
           });
+
+  static boolean classMetadataUnsupported() {
+    // https://github.com/google/truth/issues/198
+    // TODO(cpovirk): Consider whether to remove instanceof tests under GWT entirely.
+    // TODO(cpovirk): Run more Truth tests under GWT, and add tests for this.
+    return false;
+  }
 }
diff --git a/core/src/main/java/com/google/common/truth/Subject.java b/core/src/main/java/com/google/common/truth/Subject.java
index 94d9e1692..bcb8e4d0d 100644
--- a/core/src/main/java/com/google/common/truth/Subject.java
+++ b/core/src/main/java/com/google/common/truth/Subject.java
@@ -299,7 +299,7 @@ public void isInstanceOf(Class<?> clazz) {
       return;
     }
     if (!isInstanceOfType(actual, clazz)) {
-      if (classMetadataUnsupported()) {
+      if (Platform.classMetadataUnsupported()) {
         throw new UnsupportedOperationException(
             actualCustomStringRepresentation()
                 + ", an instance of "
@@ -320,7 +320,7 @@ public void isNotInstanceOf(Class<?> clazz) {
     if (clazz == null) {
       throw new NullPointerException("clazz");
     }
-    if (classMetadataUnsupported()) {
+    if (Platform.classMetadataUnsupported()) {
       throw new UnsupportedOperationException(
           "isNotInstanceOf is not supported under -XdisableClassMetadata");
     }
@@ -1185,13 +1185,6 @@ private static String typeDescriptionOrGuess(
     return UPPER_CAMEL.to(LOWER_CAMEL, actualClass);
   }
 
-  private static boolean classMetadataUnsupported() {
-    // https://github.com/google/truth/issues/198
-    // TODO(cpovirk): Consider whether to remove instanceof tests under GWT entirely.
-    // TODO(cpovirk): Run more Truth tests under GWT, and add tests for this.
-    return String.class.getSuperclass() == null;
-  }
-
   private void doFail(ImmutableList<Fact> facts) {
     checkNotNull(metadata).fail(facts);
   }
diff --git a/core/src/main/java/com/google/common/truth/super/com/google/common/truth/Platform.java b/core/src/main/java/com/google/common/truth/super/com/google/common/truth/Platform.java
index 4642f8ab9..3bb24af2e 100644
--- a/core/src/main/java/com/google/common/truth/super/com/google/common/truth/Platform.java
+++ b/core/src/main/java/com/google/common/truth/super/com/google/common/truth/Platform.java
@@ -268,5 +268,9 @@ static boolean isKotlinRange(Iterable<?> iterable) {
   static boolean kotlinRangeContains(Iterable<?> haystack, @Nullable Object needle) {
     throw new AssertionError(); // never called under GWT because isKotlinRange returns false
   }
+
+  static boolean classMetadataUnsupported() {
+    return String.class.getSuperclass() == null;
+  }
 }