diff --git a/unicodetools/src/main/java/org/unicode/text/UCD/TestUnicodeInvariants.java b/unicodetools/src/main/java/org/unicode/text/UCD/TestUnicodeInvariants.java
index ac507c58ed..c14f487219 100644
--- a/unicodetools/src/main/java/org/unicode/text/UCD/TestUnicodeInvariants.java
+++ b/unicodetools/src/main/java/org/unicode/text/UCD/TestUnicodeInvariants.java
@@ -184,7 +184,7 @@ public static int testInvariants(String inputFile, String suffix, boolean doRang
                 }
                 final var noComments = new StringBuilder();
                 final List<String> lines = new ArrayList<>();
-                final List<Integer> lineBeginnings = new ArrayList();
+                final List<Integer> lineBeginnings = new ArrayList<>();
                 try (final BufferedReader in = getInputReader(inputFile)) {
                     in.lines()
                             .forEach(
@@ -233,8 +233,8 @@ public static int testInvariants(String inputFile, String suffix, boolean doRang
                 final Function<ParsePosition, Integer> getLineNumber =
                         position -> {
                             for (int i = 0; i < lineBeginnings.size(); ++i) {
-                                if (lineBeginnings.get(i) > position.getIndex()) {
-                                    return i; // 1-based line number.
+                                if (lineBeginnings.get(i) >= position.getIndex()) {
+                                    return i + 1; // 1-based line number.
                                 }
                             }
                             return lineBeginnings.size();