diff --git a/plugins/header_rewrite/header_rewrite_test.cc b/plugins/header_rewrite/header_rewrite_test.cc
index 7ec83230a36..36702c1761f 100644
--- a/plugins/header_rewrite/header_rewrite_test.cc
+++ b/plugins/header_rewrite/header_rewrite_test.cc
@@ -557,6 +557,24 @@ test_tokenizer()
     END_TEST();
   }
 
+  {
+    SimpleTokenizerTest p("{a}%{PATH}");
+    CHECK_EQ(p.get_tokens().size(), 2UL);
+    CHECK_EQ(p.get_tokens()[0], "{a}");
+    CHECK_EQ(p.get_tokens()[1], "%{PATH}");
+
+    END_TEST();
+  }
+
+  {
+    SimpleTokenizerTest p("<a>%{PATH}");
+    CHECK_EQ(p.get_tokens().size(), 2UL);
+    CHECK_EQ(p.get_tokens()[0], "<a>");
+    CHECK_EQ(p.get_tokens()[1], "%{PATH}");
+
+    END_TEST();
+  }
+
   return errors;
 }
 
diff --git a/plugins/header_rewrite/parser.cc b/plugins/header_rewrite/parser.cc
index c1f467d39a8..ed3a7e27da1 100644
--- a/plugins/header_rewrite/parser.cc
+++ b/plugins/header_rewrite/parser.cc
@@ -344,7 +344,7 @@ HRWSimpleTokenizer::HRWSimpleTokenizer(const std::string &line)
     switch (state) {
     case PARSER_DEFAULT:
       if ((line[i] == '{') || (line[i] == '<')) {
-        if (line[i - 1] == '%') {
+        if (i > 0 && line[i - 1] == '%') {
           // pickup what we currently have
           cur_token_length = i - cur_token_start - 1;
           if (cur_token_length > 0) {