diff --git a/src/main/groovy/io/repaint/maven/tiles/TileValidator.groovy b/src/main/groovy/io/repaint/maven/tiles/TileValidator.groovy
index 61fe8ad..e9ea50b 100644
--- a/src/main/groovy/io/repaint/maven/tiles/TileValidator.groovy
+++ b/src/main/groovy/io/repaint/maven/tiles/TileValidator.groovy
@@ -112,6 +112,21 @@ class TileValidator {
 			validModel = null
 		}
 
+		if (model.build?.extensions) {
+			log.error("Tile has extensions and must not have")
+			validModel = null
+		}
+
+		if (model.build?.plugins) {
+			for (plugin in model.build.plugins) {
+				if (plugin.extensions) {
+					log.error("Tile has plugins with extensions and must not have")
+					validModel = null
+					break
+				}
+			}
+		}
+
 		return validModel
 	}
 }
diff --git a/src/test/groovy/io/repaint/maven/tiles/TileValidatorTest.groovy b/src/test/groovy/io/repaint/maven/tiles/TileValidatorTest.groovy
index aef3ff2..fb19567 100644
--- a/src/test/groovy/io/repaint/maven/tiles/TileValidatorTest.groovy
+++ b/src/test/groovy/io/repaint/maven/tiles/TileValidatorTest.groovy
@@ -31,7 +31,7 @@ class TileValidatorTest {
 	public void testValidation() {
 		new TileValidator().loadModel(logger, new File("src/test/resources/bad-tile.xml"), "")
 
-		assert errors.size() == 8
+		assert errors.size() == 10
 		assert warnings.size() == 0
 		assert infos.size() == 0
 	}
diff --git a/src/test/resources/bad-tile.xml b/src/test/resources/bad-tile.xml
index 00d8529..aa1279a 100644
--- a/src/test/resources/bad-tile.xml
+++ b/src/test/resources/bad-tile.xml
@@ -51,5 +51,21 @@
 				</plugin>
 			</plugins>
 		</pluginManagement>
+		<plugins>
+			<plugin>
+				<groupId>group</groupId>
+				<artifactId>artifact</artifactId>
+				<version>version</version>
+				<extensions>true</extensions>
+			</plugin>
+		</plugins>
+		<extensions>
+			<extension>
+				<groupId>group</groupId>
+				<artifactId>artifact</artifactId>
+				<version>version</version>
+			</extension>
+		</extensions>
 	</build>
+
 </project>