diff --git a/README.md b/README.md
index 5f86065..37c17ab 100644
--- a/README.md
+++ b/README.md
@@ -33,7 +33,7 @@ Add these lines to your `pom.xml`.
 <dependency>
   <groupId>com.github.f4b6a3</groupId>
   <artifactId>ulid-creator</artifactId>
-  <version>2.3.1</version>
+  <version>2.3.2</version>
 </dependency>
 ```
 See more options in [maven.org](https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator).
diff --git a/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java b/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java
index 846de8a..04b32e5 100644
--- a/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java
+++ b/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java
@@ -30,9 +30,6 @@ import static com.github.f4b6a3.ulid.util.internal.UlidStruct.BASE32_VALUES;
 
 public final class UlidValidator {
 
-	// Date: 10889-08-02T05:31:50.655Z: 281474976710655 (2^48-1)
-	private static final long TIMESTAMP_MAX = 0xffffffffffffL;
-
 	protected static final int ULID_LENGTH = 26;
 
 	private UlidValidator() {
@@ -58,11 +55,7 @@ public final class UlidValidator {
 	 * @return boolean true if valid
 	 */
 	public static boolean isValid(String ulid) {
-		if (ulid == null) {
-			return false;
-		}
-		char[] chars = ulid.toCharArray();
-		return isValidString(chars) && isValidTimestamp(chars);
+		return (ulid != null && ulid.length() != 0 && isValidString(ulid.toCharArray()));
 	}
 
 	/**
@@ -74,13 +67,9 @@ public final class UlidValidator {
 	 * @throws InvalidUlidException if invalid
 	 */
 	public static void validate(String ulid) {
-		if(ulid != null) {
-			final char[] chars = ulid.toCharArray();
-			if(isValidString(chars) && isValidTimestamp(chars)) {
-				return; // valid
-			}
+		if (ulid == null || ulid.length() == 0 || !isValidString(ulid.toCharArray())) {
+			throw new InvalidUlidException(String.format("Invalid ULID: %s.", ulid));
 		}
-		throw new InvalidUlidException(String.format("Invalid ULID: %s.", ulid));
 	}
 
 	/**
@@ -101,6 +90,12 @@ public final class UlidValidator {
 	 * @return boolean true if valid
 	 */
 	protected static boolean isValidString(final char[] c) {
+
+		// the two extra bits added by base-32 encoding must be zero
+		if ((BASE32_VALUES[c[0]] & 0b11000) != 0) {
+			return false; // overflow
+		}
+
 		int hyphen = 0;
 		for (int i = 0; i < c.length; i++) {
 			if (c[i] == '-') {
@@ -117,28 +112,4 @@ public final class UlidValidator {
 		}
 		return (c.length - hyphen) == ULID_LENGTH;
 	}
-
-	/**
-	 * Checks if the timestamp is between 0 and 2^48-1
-	 * 
-	 * @param chars a char array
-	 * @return false if invalid.
-	 */
-	protected static boolean isValidTimestamp(char[] chars) {
-
-		long time = 0;
-
-		time |= BASE32_VALUES[chars[0x00]] << 45;
-		time |= BASE32_VALUES[chars[0x01]] << 40;
-		time |= BASE32_VALUES[chars[0x02]] << 35;
-		time |= BASE32_VALUES[chars[0x03]] << 30;
-		time |= BASE32_VALUES[chars[0x04]] << 25;
-		time |= BASE32_VALUES[chars[0x05]] << 20;
-		time |= BASE32_VALUES[chars[0x06]] << 15;
-		time |= BASE32_VALUES[chars[0x07]] << 10;
-		time |= BASE32_VALUES[chars[0x08]] << 5;
-		time |= BASE32_VALUES[chars[0x09]];
-
-		return time >= 0 && time <= TIMESTAMP_MAX;
-	}
 }
diff --git a/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java b/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
index c17e847..e017393 100644
--- a/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
@@ -55,9 +55,19 @@ public class UlidUtilTest {
 		ulid = "7ZZZZZZZZZ" + EXAMPLE_RANDOMNESS;
 		milliseconds = extractUnixMilliseconds(ulid);
 		assertEquals(TIMESTAMP_MAX, milliseconds);
-
+		
 		try {
-			ulid = "8ZZZZZZZZZ" + EXAMPLE_RANDOMNESS;
+			// Test the first extra bit added by the base32 encoding
+			ulid = "G0000000000000000000000000";
+			extractUnixMilliseconds(ulid);
+			fail("Should throw an InvalidUlidException");
+		} catch (InvalidUlidException e) {
+			// success
+		}
+		
+		try {
+			// Test the second extra bit added by the base32 encoding
+			ulid = "80000000000000000000000000";
 			extractUnixMilliseconds(ulid);
 			fail("Should throw an InvalidUlidException");
 		} catch (InvalidUlidException e) {
@@ -77,14 +87,6 @@ public class UlidUtilTest {
 		ulid = UlidConverter.fromString(string);
 		milliseconds = extractUnixMilliseconds(ulid);
 		assertEquals(TIMESTAMP_MAX, milliseconds);
-
-		try {
-			string = "8ZZZZZZZZZ" + EXAMPLE_RANDOMNESS;
-			ulid = UlidConverter.fromString(string);
-			fail("Should throw an InvalidUlidException");
-		} catch (InvalidUlidException e) {
-			// success
-		}
 	}
 
 	@Test