diff --git a/src/main/kotlin/org/vineflower/ijplugin/VineflowerDecompilerBase.kt b/src/main/kotlin/org/vineflower/ijplugin/VineflowerDecompilerBase.kt
index 7f4d7c6..48d6c22 100644
--- a/src/main/kotlin/org/vineflower/ijplugin/VineflowerDecompilerBase.kt
+++ b/src/main/kotlin/org/vineflower/ijplugin/VineflowerDecompilerBase.kt
@@ -59,6 +59,10 @@ abstract class VineflowerDecompilerBase : ClassFileDecompilers.Full() {
     abstract val sourceFileType: FileType
 
     override fun accepts(file: VirtualFile): Boolean {
+        if (file.extension != "class") {
+            return false
+        }
+
         val state = VineflowerState.getInstance()
         if (!state.enabled || state.hadError) {
             return false
diff --git a/src/main/kotlin/org/vineflower/ijplugin/VineflowerInvoker.kt b/src/main/kotlin/org/vineflower/ijplugin/VineflowerInvoker.kt
index d2fb171..f984424 100644
--- a/src/main/kotlin/org/vineflower/ijplugin/VineflowerInvoker.kt
+++ b/src/main/kotlin/org/vineflower/ijplugin/VineflowerInvoker.kt
@@ -14,6 +14,7 @@ import com.intellij.openapi.vfs.readBytes
 import com.intellij.psi.JavaPsiFacade
 import com.intellij.psi.PsiClass
 import com.intellij.psi.search.GlobalSearchScope
+import com.intellij.util.ArrayUtil
 import java.io.File
 import java.util.concurrent.CompletableFuture
 import java.util.concurrent.LinkedBlockingQueue
@@ -250,7 +251,14 @@ class VineflowerInvoker(classLoader: ClassLoader) {
         private val getCurrentDecompContext = classLoader.loadClass("org.jetbrains.java.decompiler.main.DecompilerContext")
             .getMethod("getCurrentContext")
 
-        fun getLanguage(bytes: ByteArray): String {
+        private val cafebabe = listOf(0xCA, 0xFE, 0xBA, 0xBE).map(Int::toByte).toByteArray()
+
+        fun getLanguage(bytes: ByteArray): String? {
+            if (ArrayUtil.startsWith(bytes, cafebabe)) {
+                // Non-class file
+                return null
+            }
+
             // ensure a decompilation context is available (otherwise the structclass constructor will fail)
             if (getCurrentDecompContext.invoke(null) == null) {
                 val empty = emptyMap<Nothing, Nothing>()