diff --git a/History.md b/History.md
index 5fa2c375..9ff0d386 100644
--- a/History.md
+++ b/History.md
@@ -1,3 +1,9 @@
+2.6.0
+=======
+
+- Import of ZF1 invoices (thanks to Stefan Schmaltz https://github.com/ZUGFeRD/mustangproject/pull/292) 
+- works again in Java 1.8 (#286)
+
 2.5.6
 =======
 2022-09-22
diff --git a/Mustang-CLI/pom.xml b/Mustang-CLI/pom.xml
index 48a4a421..6fdcf8c9 100644
--- a/Mustang-CLI/pom.xml
+++ b/Mustang-CLI/pom.xml
@@ -13,6 +13,9 @@
    <version>2.5.7-SNAPSHOT</version>
    <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+      <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
+      <maven.compiler.source>1.8</maven.compiler.source>
+      <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
       <dependency>
@@ -84,6 +87,26 @@
                </archive>
             </configuration>
          </plugin>
+         <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-toolchains-plugin</artifactId>
+            <version>3.1.0</version>
+            <executions>
+               <execution>
+                  <goals>
+                     <goal>toolchain</goal>
+                  </goals>
+               </execution>
+            </executions>
+            <configuration>
+               <toolchains>
+                  <jdk>
+                     <version>1.8</version>
+                     <vendor>sun</vendor>
+                  </jdk>
+               </toolchains>
+            </configuration>
+         </plugin>
          <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
diff --git a/doc/development_documentation.md b/doc/development_documentation.md
index 4ceda7ad..13c05e78 100644
--- a/doc/development_documentation.md
+++ b/doc/development_documentation.md
@@ -154,12 +154,38 @@ The whole settings.xml then looks e.g. like this
 The TOKEN is generated on github.
 Deployment to maven central is described e.g. on [dzone](https://dzone.com/articles/publish-your-artifacts-to-maven-central).
 See the following screenshot:
-
-
 Sign in in GitHub and click on the profile picture -> Settings. Now just generate a new token and set the checkboxes from the screenshot.
 ![screenshot](development_documentation_screenshot_github_settings.png "Screenshot Github Settings")
  The Token-ID is the password. 
 
+In .m2 also need a toolchains.xml which defines a Sun JDK 1.8 target like the following: 
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<toolchains>
+  <!-- JDK toolchains -->
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>1.8</version>
+      <vendor>sun</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>C:\Program Files\Java\jdk1.8.0_341</jdkHome>
+    </configuration>
+  </toolchain>
+  <toolchain>
+    <type>jdk</type>
+    <provides>
+      <version>18</version>
+      <vendor>zulu</vendor>
+    </provides>
+    <configuration>
+      <jdkHome>C:\Program Files\Zulu\zulu-18\</jdkHome>
+    </configuration>
+  </toolchain>
+ 
+</toolchains>
+```
 
 ## Integrate before release
 
diff --git a/library/pom.xml b/library/pom.xml
index c18ec025..8b7b1706 100644
--- a/library/pom.xml
+++ b/library/pom.xml
@@ -142,6 +142,26 @@
 					<target>1.8</target>
 				</configuration>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-toolchains-plugin</artifactId>
+				<version>3.1.0</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>toolchain</goal>
+						</goals>
+					</execution>
+				</executions>
+				<configuration>
+					<toolchains>
+						<jdk>
+							<version>1.8</version>
+							<vendor>sun</vendor>
+						</jdk>
+					</toolchains>
+				</configuration>
+			</plugin>
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-shade-plugin</artifactId>
diff --git a/validator/pom.xml b/validator/pom.xml
index 6876f540..bab6f01f 100644
--- a/validator/pom.xml
+++ b/validator/pom.xml
@@ -29,6 +29,9 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.deploy.skip>false
         </maven.deploy.skip><!-- do deploy to maven central, parent project does not and inherits -->
+        <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
 
     </properties>
     <dependencies>
@@ -125,8 +128,6 @@
             </plugins>
         </pluginManagement>
         <plugins>
-
-
             <!-- allow getImplementationVersion for the pom.xml -->
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -141,7 +142,26 @@
                     </archive>
                 </configuration>
             </plugin>
-            <!-- ZUV -->
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-toolchains-plugin</artifactId>
+                <version>3.1.0</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>toolchain</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <toolchains>
+                        <jdk>
+                            <version>1.8</version>
+                            <vendor>sun</vendor>
+                        </jdk>
+                    </toolchains>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
@@ -153,8 +173,8 @@
                     <!-- http://stackoverflow.com/questions/574594/how-can-i-create-an-executable-jar-with-dependencies-using-maven
                              mvn clean compile assembly:single -->
                     <!-- or whatever version you use -->
-                    <source>11</source>
-                    <target>11</target>
+                    <source>1.8</source>
+                    <target>1.8</target>
                 </configuration>
             </plugin>
             <!-- /ZUV -->