diff --git a/modules/analysis/common/src/java/org/apache/lucene/analysis/pattern/PatternTokenizer.java b/modules/analysis/common/src/java/org/apache/lucene/analysis/pattern/PatternTokenizer.java
index 6aca0c5edd8..bc80391c95e 100644
--- a/modules/analysis/common/src/java/org/apache/lucene/analysis/pattern/PatternTokenizer.java
+++ b/modules/analysis/common/src/java/org/apache/lucene/analysis/pattern/PatternTokenizer.java
@@ -69,12 +69,17 @@ public final class PatternTokenizer extends Tokenizer {
     super(input);
     this.pattern = pattern;
     this.group = group;
-    fillBuffer(str, input);
-    matcher = pattern.matcher(str);
+
+    // Use "" instead of str so don't consume chars
+    // (fillBuffer) from the input on throwing IAE below:
+    matcher = pattern.matcher("");
+
     // confusingly group count depends ENTIRELY on the pattern but is only accessible via matcher
     if (group >= 0 && group > matcher.groupCount()) {
       throw new IllegalArgumentException("invalid group specified: pattern only has: " + matcher.groupCount() + " capturing groups");
     }
+    fillBuffer(str, input);
+    matcher.reset(str);
     index = 0;
   }