diff --git a/src/main/java/com/dashjoin/jsonata/Tokenizer.java b/src/main/java/com/dashjoin/jsonata/Tokenizer.java
index 503373d..1acbad3 100644
--- a/src/main/java/com/dashjoin/jsonata/Tokenizer.java
+++ b/src/main/java/com/dashjoin/jsonata/Tokenizer.java
@@ -142,7 +142,11 @@ Pattern scanRegex() {
                 start = position;
                 while (currentChar == 'i' || currentChar == 'm') {
                     position++;
-                    currentChar = path.charAt(position);
+                    if (position < length) {
+                        currentChar = path.charAt(position);
+                    } else {
+                        currentChar = 0;
+                    }
                 }
                 flags = path.substring(start, position) + 'g';
                 
diff --git a/src/test/java/com/dashjoin/jsonata/StringTest.java b/src/test/java/com/dashjoin/jsonata/StringTest.java
index 2ca01e6..5009b4d 100644
--- a/src/test/java/com/dashjoin/jsonata/StringTest.java
+++ b/src/test/java/com/dashjoin/jsonata/StringTest.java
@@ -127,6 +127,13 @@ public void evalTest() {
         + "  $eval('$data.Wert1')\n"
         + ")").evaluate(null));
   }
+
+  @Test
+  public void regexTest() {
+    Assertions.assertEquals(Map.of("foo", 1), jsonata(
+        "($matcher := $eval('/^' & 'foo' & '/i'); $.$spread()[$.$keys() ~> $matcher])")
+        .evaluate(Map.of("foo", 1, "bar", 2)));
+  }
   
   @Disabled
   @Test