diff --git a/org.eclipse.jgit.test/pom.xml b/org.eclipse.jgit.test/pom.xml
index 6db6a8104..c2fd83ed9 100644
--- a/org.eclipse.jgit.test/pom.xml
+++ b/org.eclipse.jgit.test/pom.xml
@@ -153,7 +153,7 @@
       <plugin>
         <artifactId>maven-surefire-plugin</artifactId>
         <configuration>
-          <argLine>-Xmx256m -Dfile.encoding=UTF-8 -Djava.io.tmpdir=${project.build.directory}</argLine>
+          <argLine>-Xmx1024m -Dfile.encoding=UTF-8 -Djava.io.tmpdir=${project.build.directory}</argLine>
           <includes>
             <include>**/*Test.java</include>
             <include>**/*Tests.java</include>
diff --git a/org.eclipse.jgit.test/tests.bzl b/org.eclipse.jgit.test/tests.bzl
index b1b7b7a9d..64dfe071c 100644
--- a/org.eclipse.jgit.test/tests.bzl
+++ b/org.eclipse.jgit.test/tests.bzl
@@ -42,6 +42,10 @@ def tests(tests):
         '//lib:jsch',
       ]
 
+    heap_size = "-Xmx256m"
+    if src.endswith("HugeCommitMessageTest.java"):
+      heap_size = "-Xmx512m"
+
     junit_tests(
       name = name,
       tags = labels,
@@ -57,5 +61,5 @@ def tests(tests):
         '//org.eclipse.jgit.lfs:jgit-lfs',
       ],
       flaky = flaky,
-      jvm_flags = ["-Xmx256m", "-Dfile.encoding=UTF-8"],
+      jvm_flags = [heap_size, "-Dfile.encoding=UTF-8"],
     )
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/HugeCommitMessageTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/HugeCommitMessageTest.java
new file mode 100644
index 000000000..4193c4ba3
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/HugeCommitMessageTest.java
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.lib;
+
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.junit.RepositoryTestCase;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.storage.file.WindowCacheConfig;
+import org.eclipse.jgit.storage.pack.PackConfig;
+import org.junit.Test;
+
+public class HugeCommitMessageTest extends RepositoryTestCase {
+
+	private static final int HUGE_SIZE = Math.max(15 * WindowCacheConfig.MB,
+			PackConfig.DEFAULT_BIG_FILE_THRESHOLD + WindowCacheConfig.MB);
+	// Larger than the 5MB fallback limit in RevWalk.getCachedBytes(RevObject
+	// obj, ObjectLoader ldr), and also larger than the default
+	// streamFileThreshold.
+
+	@Test
+	public void testHugeCommitMessage() throws Exception {
+		try (Git git = new Git(db)) {
+			writeTrashFile("foo", "foo");
+			git.add().addFilepattern("foo").call();
+			WindowCacheConfig wc = new WindowCacheConfig();
+			wc.setStreamFileThreshold(HUGE_SIZE + WindowCacheConfig.MB);
+			wc.install();
+			RevCommit commit = git.commit()
+					.setMessage(insanelyHugeCommitMessage()).call();
+			Ref master = db.findRef("master");
+			List<Ref> actual = git.branchList().setContains(commit.getName())
+					.call();
+			assertTrue("Should be contained in branch master",
+					actual.contains(master));
+		}
+	}
+
+	private String insanelyHugeCommitMessage() {
+		final String oneLine = "012345678901234567890123456789012345678901234567890123456789\n";
+		StringBuilder b = new StringBuilder(HUGE_SIZE + oneLine.length());
+		// Give the message a real header; otherwise even writing the reflog
+		// message may run into troubles because RevCommit.getShortMessage()
+		// will return the whole message.
+		b.append("An insanely huge commit message\n\n");
+		while (b.length() < HUGE_SIZE) {
+			b.append(oneLine);
+		}
+		return b.toString();
+	}
+
+}