diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
index f6ae4c48ea..3f8b2d5802 100644
--- a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
@@ -339,26 +339,34 @@ public class JarWriter implements LoaderClassesWriter, AutoCloseable {
 	/**
 	 * {@link InputStream} that can peek ahead at zip header bytes.
 	 */
-	private static class ZipHeaderPeekInputStream extends FilterInputStream {
+	static class ZipHeaderPeekInputStream extends FilterInputStream {
 
 		private static final byte[] ZIP_HEADER = new byte[] { 0x50, 0x4b, 0x03, 0x04 };
 
 		private final byte[] header;
 
+		private final int headerLength;
+
+		private int position;
+
 		private ByteArrayInputStream headerStream;
 
 		protected ZipHeaderPeekInputStream(InputStream in) throws IOException {
 			super(in);
 			this.header = new byte[4];
-			int len = in.read(this.header);
-			this.headerStream = new ByteArrayInputStream(this.header, 0, len);
+			this.headerLength = in.read(this.header);
+			this.headerStream = new ByteArrayInputStream(this.header, 0,
+					this.headerLength);
 		}
 
 		@Override
 		public int read() throws IOException {
 			int read = (this.headerStream != null ? this.headerStream.read() : -1);
 			if (read != -1) {
-				this.headerStream = null;
+				this.position++;
+				if (this.position >= this.headerLength) {
+					this.headerStream = null;
+				}
 				return read;
 			}
 			return super.read();
@@ -373,11 +381,20 @@ public class JarWriter implements LoaderClassesWriter, AutoCloseable {
 		public int read(byte[] b, int off, int len) throws IOException {
 			int read = (this.headerStream != null ? this.headerStream.read(b, off, len)
 					: -1);
-			if (read != -1) {
-				this.headerStream = null;
-				return read;
+			if (read > 0) {
+				this.position += read;
 			}
-			return super.read(b, off, len);
+			else {
+				read = 0;
+			}
+			if (read < len) {
+				read += super.read(b, off + read, len - read);
+				this.position += read;
+			}
+			if (this.position >= this.headerLength) {
+				this.headerStream = null;
+			}
+			return read;
 		}
 
 		public boolean hasZipHeader() {
diff --git a/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/ZipHeaderPeekInputStreamTests.java b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/ZipHeaderPeekInputStreamTests.java
new file mode 100644
index 0000000000..5ca8d55e14
--- /dev/null
+++ b/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/ZipHeaderPeekInputStreamTests.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.loader.tools;
+
+/**
+ * Tests for {@link ZipHeaderPeekInputStream}.
+ *
+ * @author Andy Wilkinson
+ */
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+
+import org.junit.Test;
+
+import org.springframework.boot.loader.tools.JarWriter.ZipHeaderPeekInputStream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ZipHeaderPeekInputStreamTests {
+
+	@Test
+	public void hasZipHeaderReturnsTrueWhenStreamStartsWithZipHeader()
+			throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0x50, 0x4b, 0x03, 0x04, 5, 6 }));) {
+			assertThat(in.hasZipHeader()).isTrue();
+		}
+	}
+
+	@Test
+	public void hasZipHeaderReturnsFalseWheStreamDoesNotStartWithZipHeader()
+			throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0, 1, 2, 3, 4, 5 }))) {
+			assertThat(in.hasZipHeader()).isFalse();
+		}
+	}
+
+	@Test
+	public void readIndividualBytes() throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0, 1, 2, 3, 4, 5 }))) {
+			assertThat(in.read()).isEqualTo(0);
+			assertThat(in.read()).isEqualTo(1);
+			assertThat(in.read()).isEqualTo(2);
+			assertThat(in.read()).isEqualTo(3);
+			assertThat(in.read()).isEqualTo(4);
+			assertThat(in.read()).isEqualTo(5);
+		}
+	}
+
+	@Test
+	public void readMultipleBytes() throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0, 1, 2, 3, 4, 5 }))) {
+			byte[] bytes = new byte[3];
+			assertThat(in.read(bytes)).isEqualTo(3);
+			assertThat(bytes).containsExactly(0, 1, 2);
+			assertThat(in.read(bytes)).isEqualTo(3);
+			assertThat(bytes).containsExactly(3, 4, 5);
+			assertThat(in.read(bytes)).isEqualTo(-1);
+		}
+	}
+
+	@Test
+	public void readingMoreThanEntireStreamReadsToEndOfStream() throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0, 1, 2, 3, 4, 5 }))) {
+			byte[] bytes = new byte[8];
+			assertThat(in.read(bytes)).isEqualTo(6);
+			assertThat(bytes).containsExactly(0, 1, 2, 3, 4, 5, 0, 0);
+			assertThat(in.read(bytes)).isEqualTo(-1);
+		}
+	}
+
+	@Test
+	public void readOfSomeOfTheHeaderThenMoreThanEntireStreamReadsToEndOfStream()
+			throws IOException {
+		try (ZipHeaderPeekInputStream in = new ZipHeaderPeekInputStream(
+				new ByteArrayInputStream(new byte[] { 0, 1, 2, 3, 4, 5 }))) {
+			byte[] bytes = new byte[8];
+			assertThat(in.read(bytes, 0, 3)).isEqualTo(3);
+			assertThat(bytes).containsExactly(0, 1, 2, 0, 0, 0, 0, 0);
+			assertThat(in.read(bytes, 3, 5)).isEqualTo(3);
+			assertThat(bytes).containsExactly(0, 1, 2, 3, 4, 5, 0, 0);
+		}
+	}
+
+}