diff --git a/wire-compiler/api/wire-compiler.api b/wire-compiler/api/wire-compiler.api
index 3c4adee9a2..fa8a348576 100644
--- a/wire-compiler/api/wire-compiler.api
+++ b/wire-compiler/api/wire-compiler.api
@@ -8,7 +8,7 @@ public final class com/squareup/wire/DryRunFileSystem : okio/ForwardingFileSyste
 public final class com/squareup/wire/WireCompiler {
 	public static final field CODE_GENERATED_BY_WIRE Ljava/lang/String;
 	public static final field Companion Lcom/squareup/wire/WireCompiler$Companion;
-	public synthetic fun <init> (Lokio/FileSystem;Lcom/squareup/wire/WireLogger;Ljava/util/List;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/util/List;Ljava/util/List;Ljava/util/List;Ljava/util/Map;ZZZZZZZZIZZZLcom/squareup/wire/kotlin/RpcCallStyle;Lcom/squareup/wire/kotlin/RpcRole;ZLjava/lang/String;ZZZZLcom/squareup/wire/kotlin/EnumMode;Ljava/util/List;Ljava/util/Map;Ljava/util/List;IILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public synthetic fun <init> (Lokio/FileSystem;Lcom/squareup/wire/WireLogger;Ljava/util/List;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;Ljava/util/List;Ljava/util/List;Ljava/util/List;ZLjava/util/Map;ZZZZZZZZIZZZLcom/squareup/wire/kotlin/RpcCallStyle;Lcom/squareup/wire/kotlin/RpcRole;ZLjava/lang/String;ZZZZLcom/squareup/wire/kotlin/EnumMode;Ljava/util/List;Ljava/util/Map;Ljava/util/List;IILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public final fun compile ()V
 	public static final fun forArgs (Ljava/nio/file/FileSystem;Lcom/squareup/wire/WireLogger;[Ljava/lang/String;)Lcom/squareup/wire/WireCompiler;
 	public static final fun forArgs (Lokio/FileSystem;Lcom/squareup/wire/WireLogger;[Ljava/lang/String;)Lcom/squareup/wire/WireCompiler;
@@ -44,6 +44,7 @@ public final class com/squareup/wire/WireCompiler {
 	public final fun getOpaqueTypes ()Ljava/util/List;
 	public final fun getPermitPackageCycles ()Z
 	public final fun getProtoPaths ()Ljava/util/List;
+	public final fun getRejectUnusedRootsOrPrunes ()Z
 	public final fun getSchemaHandlerFactoryClass ()Ljava/lang/String;
 	public final fun getSourceFileNames ()Ljava/util/List;
 	public final fun getSwiftExclusive ()Z
diff --git a/wire-compiler/src/main/java/com/squareup/wire/WireCompiler.kt b/wire-compiler/src/main/java/com/squareup/wire/WireCompiler.kt
index 2b130afba0..fa55747a77 100644
--- a/wire-compiler/src/main/java/com/squareup/wire/WireCompiler.kt
+++ b/wire-compiler/src/main/java/com/squareup/wire/WireCompiler.kt
@@ -128,6 +128,7 @@ class WireCompiler internal constructor(
   val sourceFileNames: List<String>,
   val treeShakingRoots: List<String>,
   val treeShakingRubbish: List<String>,
+  val rejectUnusedRootsOrPrunes: Boolean,
   val modules: Map<String, WireRun.Module>,
   val emitAndroid: Boolean,
   val emitAndroidAnnotations: Boolean,
@@ -230,6 +231,7 @@ class WireCompiler internal constructor(
       permitPackageCycles = permitPackageCycles,
       loadExhaustively = loadExhaustively,
       eventListeners = eventListenerFactoryClasses.map { newEventListenerFactory(it).create() },
+      rejectUnusedRootsOrPrunes = rejectUnusedRootsOrPrunes,
       opaqueTypes = opaqueTypes,
     )
 
@@ -301,6 +303,7 @@ class WireCompiler internal constructor(
     private const val KOTLIN_ENUM_MODE = "--kotlin_enum_mode="
     private const val CUSTOM_OPTION_FLAG = "--custom_option="
     private const val OPAQUE_TYPES_FLAG = "--opaque_types="
+    private const val IGNORE_UNUSED_ROOTS_AND_PRUNES = "--ignore_unused_roots_and_prunes"
     private const val KOTLIN_EXPLICIT_STREAMING_CALLS = "--kotlin_explicit_streaming_calls"
 
     @Throws(IOException::class)
@@ -369,6 +372,7 @@ class WireCompiler internal constructor(
       var kotlinExplicitStreamingCalls = false
       var dryRun = false
       val customOptions = mutableMapOf<String, String>()
+      var rejectUnusedRootsOrPrunes = true
       val opaqueTypes = mutableListOf<String>()
 
       for (arg in args) {
@@ -492,6 +496,7 @@ class WireCompiler internal constructor(
           arg == JAVA_INTEROP -> javaInterop = true
           arg == EMIT_PROTO_READER_32 -> emitProtoReader32 = true
           arg == KOTLIN_EXPLICIT_STREAMING_CALLS -> kotlinExplicitStreamingCalls = true
+          arg == IGNORE_UNUSED_ROOTS_AND_PRUNES -> rejectUnusedRootsOrPrunes = false
           arg.startsWith("--") -> throw IllegalArgumentException("Unknown argument '$arg'.")
           else -> sourceFileNames.add(arg)
         }
@@ -547,6 +552,7 @@ class WireCompiler internal constructor(
         eventListenerFactoryClasses = eventListenerFactoryClasses,
         customOptions = customOptions,
         opaqueTypes = opaqueTypes,
+        rejectUnusedRootsOrPrunes = rejectUnusedRootsOrPrunes,
         kotlinExplicitStreamingCalls = kotlinExplicitStreamingCalls,
       )
     }
diff --git a/wire-compiler/src/test/java/com/squareup/wire/CommandLineOptionsTest.kt b/wire-compiler/src/test/java/com/squareup/wire/CommandLineOptionsTest.kt
index e4d62a0c81..8f4c44fbad 100644
--- a/wire-compiler/src/test/java/com/squareup/wire/CommandLineOptionsTest.kt
+++ b/wire-compiler/src/test/java/com/squareup/wire/CommandLineOptionsTest.kt
@@ -21,6 +21,7 @@ import assertk.assertions.containsOnly
 import assertk.assertions.hasMessage
 import assertk.assertions.isEmpty
 import assertk.assertions.isEqualTo
+import assertk.assertions.isFalse
 import com.squareup.wire.kotlin.EnumMode
 import com.squareup.wire.schema.WireRun
 import java.io.File
@@ -112,6 +113,9 @@ class CommandLineOptionsTest {
 
     compiler = parseArgs("--java_out=.", "--includes=com.example.Foo,com.example.Bar")
     assertThat(compiler.treeShakingRoots).containsExactly("com.example.Foo", "com.example.Bar")
+
+    compiler = parseArgs("--java_out=.", "--ignore_unused_roots_and_prunes")
+    assertThat(compiler.rejectUnusedRootsOrPrunes).isFalse()
   }
 
   @Test