diff --git a/src/main/java/biweekly/util/DataUri.java b/src/main/java/biweekly/util/DataUri.java
index cc471395..f2237135 100644
--- a/src/main/java/biweekly/util/DataUri.java
+++ b/src/main/java/biweekly/util/DataUri.java
@@ -41,6 +41,7 @@
  * @author Michael Angstadt
  */
 public final class DataUri {
+	private static final String SCHEME = "data:";
 	private final byte[] data;
 	private final String text;
 	private final String contentType;
@@ -95,8 +96,7 @@ private DataUri(String contentType, byte[] data, String text) {
 	public static DataUri parse(String uri) {
 		//Syntax: data:[<media type>][;charset=<character set>][;base64],<data>
 
-		String scheme = "data:";
-		if (uri.length() < scheme.length() || !uri.substring(0, scheme.length()).equalsIgnoreCase(scheme)) {
+		if (!StringUtils.startsWithIgnoreCase(uri, SCHEME)) {
 			//not a data URI
 			throw Messages.INSTANCE.getIllegalArgumentException(22);
 		}
@@ -105,8 +105,8 @@ public static DataUri parse(String uri) {
 		String charset = null;
 		boolean base64 = false;
 		String dataStr = null;
-		int tokenStart = scheme.length();
-		for (int i = scheme.length(); i < uri.length(); i++) {
+		int tokenStart = SCHEME.length();
+		for (int i = SCHEME.length(); i < uri.length(); i++) {
 			char c = uri.charAt(i);
 
 			if (c == ';') {
@@ -211,7 +211,7 @@ public String toString() {
 	 */
 	public String toString(String charset) {
 		StringBuilder sb = new StringBuilder();
-		sb.append("data:");
+		sb.append(SCHEME);
 		sb.append(contentType);
 
 		if (data != null) {
diff --git a/src/main/java/biweekly/util/StringUtils.java b/src/main/java/biweekly/util/StringUtils.java
index 194af331..741ac8de 100644
--- a/src/main/java/biweekly/util/StringUtils.java
+++ b/src/main/java/biweekly/util/StringUtils.java
@@ -86,6 +86,22 @@ public static void repeat(char c, int count, StringBuilder sb) {
 		}
 	}
 
+	/**
+	 * Like {@link String#startsWith()}, but using case-insensitive
+	 * comparison.
+	 * @param str the string
+	 * @param prefix the prefix
+	 * @return true if the string begins with the given prefix using
+	 * case-insensitive comparison, false if not
+	 */
+	public static boolean startsWithIgnoreCase(String str, String prefix) {
+		if (str.length() < prefix.length()) {
+			return false;
+		}
+
+		return str.substring(0, prefix.length()).equalsIgnoreCase(prefix);
+	}
+
 	/**
 	 * Joins a collection of values into a delimited list.
 	 * @param collection the collection of values
diff --git a/src/test/java/biweekly/util/StringUtilsTest.java b/src/test/java/biweekly/util/StringUtilsTest.java
index 27bb11eb..260997b6 100644
--- a/src/test/java/biweekly/util/StringUtilsTest.java
+++ b/src/test/java/biweekly/util/StringUtilsTest.java
@@ -1,7 +1,9 @@
 package biweekly.util;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -65,6 +67,13 @@ public void afterPrefixIgnoreCase() {
 		expected = StringUtils.afterPrefixIgnoreCase("m", "mailto:");
 		assertNull(expected);
 	}
+	
+	@Test
+	public void startsWithIgnoreCase() {
+		assertTrue(StringUtils.startsWithIgnoreCase("MAILTO:email@example.com", "mailto:"));
+		assertFalse(StringUtils.startsWithIgnoreCase("http://www.google.com", "mailto:"));
+		assertFalse(StringUtils.startsWithIgnoreCase("m", "mailto:"));
+	}
 
 	@Test
 	public void join_multiple() {