pom-plain.xml: fix syntax
diff --git a/pom-plain.xml b/pom-plain.xml
index 460b0ea..f10e63b 100644
--- a/pom-plain.xml
+++ b/pom-plain.xml
@@ -106,28 +106,30 @@
     </profile>
     <profile>
       <id>gpg</id>
-      <plugins>
-        <plugin>
-          <groupId>org.apache.maven.plugins</groupId>
-          <artifactId>maven-gpg-plugin</artifactId>
-          <version>1.6</version>
-          <executions>
-            <execution>
-              <id>sign-artifacts</id>
-              <phase>verify</phase>
-              <goals>
-                <goal>sign</goal>
-              </goals>
-              <configuration>
-                <gpgArguments>
-                  <arg>--pinentry-mode</arg>
-                  <arg>loopback</arg>
-                </gpgArguments>
-              </configuration>
-            </execution>
-          </executions>
-        </plugin>
-      </plugins>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-gpg-plugin</artifactId>
+            <version>1.6</version>
+            <executions>
+              <execution>
+                <id>sign-artifacts</id>
+                <phase>verify</phase>
+                <goals>
+                  <goal>sign</goal>
+                </goals>
+                <configuration>
+                  <gpgArguments>
+                    <arg>--pinentry-mode</arg>
+                    <arg>loopback</arg>
+                  </gpgArguments>
+                </configuration>
+              </execution>
+            </executions>
+          </plugin>
+        </plugins>
+      </build>
     </profile>
   </profiles>