diff --git a/approvaltests-tests/src/test/java/org/approvaltests/ApprovalsDuplicateVerifyExceptionTest.testExceptionMessage.approved.txt b/approvaltests-tests/src/test/java/org/approvaltests/ApprovalsDuplicateVerifyExceptionTest.testExceptionMessage.approved.txt
index b468846fb..d8e8666fe 100644
--- a/approvaltests-tests/src/test/java/org/approvaltests/ApprovalsDuplicateVerifyExceptionTest.testExceptionMessage.approved.txt
+++ b/approvaltests-tests/src/test/java/org/approvaltests/ApprovalsDuplicateVerifyExceptionTest.testExceptionMessage.approved.txt
@@ -1,11 +1,11 @@
 org.approvaltests.ApprovalsDuplicateVerifyException: Already approved: file.txt
 By default, ApprovalTests only allows one verify() call per test.
-To find out more, visit: 
+To find out more, visit:
 https://github.com/approvals/ApprovalTests.Java/blob/master/approvaltests/docs/reference/Naming.md
 
 # Fixes
 1. separate your test into two tests
 2. add NamedParameters with the NamerFactory
-3. Override Approvals.settings() with either 
-	a. allowMultipleVerifyCallsForThisClass
-	b. allowMultipleVerifyCallsForThisMethod
\ No newline at end of file
+3. Override Approvals.settings() with either
+    a. allowMultipleVerifyCallsForThisClass
+    b. allowMultipleVerifyCallsForThisMethod
\ No newline at end of file
diff --git a/approvaltests-tests/src/test/java/org/approvaltests/inline/InlineApprovalsTest.java b/approvaltests-tests/src/test/java/org/approvaltests/inline/InlineApprovalsTest.java
index 751c3afa1..a5f687c52 100644
--- a/approvaltests-tests/src/test/java/org/approvaltests/inline/InlineApprovalsTest.java
+++ b/approvaltests-tests/src/test/java/org/approvaltests/inline/InlineApprovalsTest.java
@@ -200,11 +200,11 @@ void testSemiAutomaticMessage()
   void testSemiAutomaticWithPreviousApproved()
   {
     var expected = """
-        42
-        ***** DELETE ME TO APPROVE *****
-        vvvvv PREVIOUS RESULT      vvvvv
-        41
-        """;
+      42
+      ***** DELETE ME TO APPROVE *****
+      vvvvv PREVIOUS RESULT      vvvvv
+      41
+      """;
     var options = new Options().inline(expected, InlineOptions.semiAutomaticWithPreviousApproved());
     try
     {
diff --git a/approvaltests/pom.xml b/approvaltests/pom.xml
index ccb8d555a..4b295e49f 100644
--- a/approvaltests/pom.xml
+++ b/approvaltests/pom.xml
@@ -164,6 +164,14 @@
                     </execution>
                 </executions>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>15</source>
+                    <target>15</target>
+                </configuration>
+            </plugin>
         </plugins>
     </build>
 
diff --git a/approvaltests/src/main/java/org/approvaltests/ApprovalsDuplicateVerifyException.java b/approvaltests/src/main/java/org/approvaltests/ApprovalsDuplicateVerifyException.java
index eb5119b5a..36e41f07c 100644
--- a/approvaltests/src/main/java/org/approvaltests/ApprovalsDuplicateVerifyException.java
+++ b/approvaltests/src/main/java/org/approvaltests/ApprovalsDuplicateVerifyException.java
@@ -4,11 +4,17 @@ public class ApprovalsDuplicateVerifyException extends RuntimeException
 {
   public ApprovalsDuplicateVerifyException(String file)
   {
-    super("Already approved: " + file + "\n"
-        + "By default, ApprovalTests only allows one verify() call per test.\n" + "To find out more, visit: \n"
-        + "https://github.com/approvals/ApprovalTests.Java/blob/master/approvaltests/docs/reference/Naming.md\n\n"
-        + "# Fixes\n" + "1. separate your test into two tests\n" + "2. add NamedParameters with the NamerFactory\n"
-        + "3. Override Approvals.settings() with either \n" + "\ta. allowMultipleVerifyCallsForThisClass\n"
-        + "\tb. allowMultipleVerifyCallsForThisMethod");
+    super("""
+        Already approved: %s
+        By default, ApprovalTests only allows one verify() call per test.
+        To find out more, visit:
+        https://github.com/approvals/ApprovalTests.Java/blob/master/approvaltests/docs/reference/Naming.md
+
+        # Fixes
+        1. separate your test into two tests
+        2. add NamedParameters with the NamerFactory
+        3. Override Approvals.settings() with either
+            a. allowMultipleVerifyCallsForThisClass
+            b. allowMultipleVerifyCallsForThisMethod""".formatted(file));;
   }
 }