diff --git a/src/main/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractor.java b/src/main/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractor.java
index c4a6864..4894492 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractor.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractor.java
@@ -1,5 +1,6 @@
 package com.googlesource.gerrit.plugins.hooks.util;
 
+import com.google.common.base.Strings;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
 import com.google.gerrit.reviewdb.client.PatchSet;
@@ -52,7 +53,10 @@
 
     while (matcher.find()) {
       int groupIdx = Math.min(matcher.groupCount(), 1);
-      issues.add(matcher.group(groupIdx));
+      String issueId = matcher.group(groupIdx);
+      if (!Strings.isNullOrEmpty(issueId)) {
+        issues.add(issueId);
+      }
     }
 
     return issues.toArray(new String[issues.size()]);
diff --git a/src/test/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractorTest.java b/src/test/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractorTest.java
index a6c42c7..f20e955 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractorTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/hooks/util/IssueExtractorTest.java
@@ -74,6 +74,20 @@
     assertLogMessageContains("Matching");
   }
 
+  public void testIssueIdsEmptyGroup() {
+    IssueExtractor issueExtractor = injector.getInstance(IssueExtractor.class);
+
+    expect(itsConfig.getIssuePattern()).andReturn(Pattern.compile("bug#(X*)(\\d+)"))
+        .atLeastOnce();
+
+    replayMocks();
+
+    String ret[] = issueExtractor.getIssueIds("bug#4711");
+    assertEquals("Number of found ids do not match", 0, ret.length);
+
+    assertLogMessageContains("Matching");
+  }
+
   public void testIssueIdsFullMatch() {
     IssueExtractor issueExtractor = injector.getInstance(IssueExtractor.class);