diff --git a/build.gradle b/build.gradle
index 1c08a8a..8c65cb3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,7 +7,8 @@ ext {
             jline: '2.14.5', // jline:jline
 
             junit: '5.9.2', // org.junit:junit-bom
-            jmh: '1.37' // org.openjdk.jmh:jmh-core
+            jmh: '1.37', // org.openjdk.jmh:jmh-core
+            assertj: '3.24.2' // org.assertj:assertj-core
     ]
 }
 
diff --git a/ownlang-parser/build.gradle b/ownlang-parser/build.gradle
index 0354e96..b411a92 100644
--- a/ownlang-parser/build.gradle
+++ b/ownlang-parser/build.gradle
@@ -12,6 +12,7 @@ dependencies {
     testImplementation platform("org.junit:junit-bom:${versions.junit}")
     testImplementation "org.junit.jupiter:junit-jupiter-params:${versions.junit}"
     testImplementation 'org.junit.jupiter:junit-jupiter'
+    testImplementation("org.assertj:assertj-core:${versions.assertj}")
     testImplementation "org.openjdk.jmh:jmh-core:${versions.jmh}"
     testImplementation "org.openjdk.jmh:jmh-generator-annprocess:${versions.jmh}"
     testAnnotationProcessor "org.openjdk.jmh:jmh-generator-annprocess:${versions.jmh}"
diff --git a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
index 746c5f0..7a12130 100644
--- a/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
+++ b/ownlang-parser/src/main/java/com/annimon/ownlang/parser/Lexer.java
@@ -138,10 +138,7 @@ public final class Lexer {
             else if (isOwnLangIdentifierStart(current)) tokenizeWord();
             else if (current == '`') tokenizeExtendedWord();
             else if (current == '"') tokenizeText();
-            else if (current == '#') {
-                next();
-                tokenizeHexNumber(1);
-            }
+            else if (current == '#') tokenizeHexNumber(1);
             else if (OPERATOR_CHARS.indexOf(current) != -1) {
                 tokenizeOperator();
             } else {
@@ -154,10 +151,9 @@ public final class Lexer {
     
     private void tokenizeNumber() {
         clearBuffer();
+        final Pos startPos = markPos();
         char current = peek(0);
         if (current == '0' && (peek(1) == 'x' || (peek(1) == 'X'))) {
-            next();
-            next();
             tokenizeHexNumber(2);
             return;
         }
@@ -170,11 +166,15 @@ public final class Lexer {
             buffer.append(current);
             current = next();
         }
-        addToken(TokenType.NUMBER, buffer.toString());
+        addToken(TokenType.NUMBER, buffer.toString(), startPos);
     }
     
-    private void tokenizeHexNumber(int skipped) {
+    private void tokenizeHexNumber(int skipChars) {
         clearBuffer();
+        final Pos startPos = markPos();
+        // Skip HEX prefix 0x or #
+        for (int i = 0; i < skipChars; i++) next();
+
         char current = peek(0);
         while (isHexNumber(current) || (current == '_')) {
             if (current != '_') {
@@ -185,7 +185,7 @@ public final class Lexer {
         }
         final int length = buffer.length();
         if (length > 0) {
-            addToken(TokenType.HEX_NUMBER, buffer.toString());
+            addToken(TokenType.HEX_NUMBER, buffer.toString(), startPos);
         }
     }
 
@@ -210,11 +210,13 @@ public final class Lexer {
                 return;
             }
         }
+
+        final Pos startPos = markPos();
         clearBuffer();
         while (true) {
             final String text = buffer.toString();
             if (!text.isEmpty() && !OPERATORS.containsKey(text + current)) {
-                addToken(OPERATORS.get(text));
+                addToken(OPERATORS.get(text), startPos);
                 return;
             }
             buffer.append(current);
@@ -224,6 +226,7 @@ public final class Lexer {
     
     private void tokenizeWord() {
         clearBuffer();
+        final Pos startPos = markPos();
         buffer.append(peek(0));
         char current = next();
         while (true) {
@@ -236,13 +239,14 @@ public final class Lexer {
         
         final String word = buffer.toString();
         if (KEYWORDS.containsKey(word)) {
-            addToken(KEYWORDS.get(word));
+            addToken(KEYWORDS.get(word), startPos);
         } else {
-            addToken(TokenType.WORD, word);
+            addToken(TokenType.WORD, word, startPos);
         }
     }
 
     private void tokenizeExtendedWord() {
+        final Pos startPos = markPos();
         next();// skip `
         clearBuffer();
         char current = peek(0);
@@ -254,10 +258,11 @@ public final class Lexer {
             current = next();
         }
         next(); // skip closing `
-        addToken(TokenType.WORD, buffer.toString());
+        addToken(TokenType.WORD, buffer.toString(), startPos);
     }
     
     private void tokenizeText() {
+        final Pos startPos = markPos();
         next();// skip "
         clearBuffer();
         char current = peek(0);
@@ -303,7 +308,7 @@ public final class Lexer {
         }
         next(); // skip closing "
         
-        addToken(TokenType.TEXT, buffer.toString());
+        addToken(TokenType.TEXT, buffer.toString(), startPos);
     }
     
     private void tokenizeComment() {
@@ -335,15 +340,20 @@ public final class Lexer {
     private void clearBuffer() {
         buffer.setLength(0);
     }
+
+    private Pos markPos() {
+        return new Pos(row, col);
+    }
     
     private char next() {
-        pos++;
         final char result = peek(0);
         if (result == '\n') {
             row++;
             col = 1;
         } else col++;
-        return result;
+
+        pos++;
+        return peek(0);
     }
     
     private char peek(int relativePosition) {
@@ -352,15 +362,15 @@ public final class Lexer {
         return input.charAt(position);
     }
     
-    private void addToken(TokenType type) {
-        addToken(type, "");
+    private void addToken(TokenType type, Pos startPos) {
+        addToken(type, "", startPos);
     }
     
-    private void addToken(TokenType type, String text) {
-        tokens.add(new Token(type, text, new Pos(row, col)));
+    private void addToken(TokenType type, String text, Pos startRow) {
+        tokens.add(new Token(type, text, startRow));
     }
-    
+
     private LexerException error(String text) {
-        return new LexerException(new Pos(row, col), text);
+        return new LexerException(markPos(), text);
     }
 }
diff --git a/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerPositionsTest.java b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerPositionsTest.java
new file mode 100644
index 0000000..900eaae
--- /dev/null
+++ b/ownlang-parser/src/test/java/com/annimon/ownlang/parser/LexerPositionsTest.java
@@ -0,0 +1,44 @@
+package com.annimon.ownlang.parser;
+
+import org.junit.jupiter.api.Test;
+import java.util.List;
+import static com.annimon.ownlang.parser.TokenType.*;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.tuple;
+
+class LexerPositionsTest {
+
+    @Test
+    void testMultiline() {
+        String input = """
+                x = 123
+                y = "abc"
+                """.stripIndent();
+        List<Token> result = Lexer.tokenize(input);
+
+        assertThat(result)
+                .hasSize(6)
+                .extracting(s -> s.pos().row(), s -> s.pos().col(), Token::type)
+                .containsExactly(
+                        tuple(1, 1, WORD), tuple(1, 3, EQ), tuple(1, 5, NUMBER),
+                        tuple(2, 1, WORD), tuple(2, 3, EQ), tuple(2, 5, TEXT)
+                );
+    }
+
+    @Test
+    void testMultilineText() {
+        String input = """
+                text = "line1
+                  line2
+                  line3"
+                """.stripIndent();
+        List<Token> result = Lexer.tokenize(input);
+
+        assertThat(result)
+                .hasSize(3)
+                .extracting(s -> s.pos().row(), s -> s.pos().col(), Token::type)
+                .containsExactly(
+                        tuple(1, 1, WORD), tuple(1, 6, EQ), tuple(1, 8, TEXT)
+                );
+    }
+}
\ No newline at end of file