diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifier.java b/service/src/main/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifier.java
index c475b8d7e..0cf04fee0 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifier.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifier.java
@@ -25,8 +25,6 @@ import org.whispersystems.textsecuregcm.util.UUIDUtil;
     description = "An identifier for an account based on the account's ACI"
 )
 public record AciServiceIdentifier(UUID uuid) implements ServiceIdentifier {
-  private static final String SERVICE_ID_STRING_COUNTER_NAME = MetricsUtil.name(AciServiceIdentifier.class, "serviceIdString");
-
   private static final IdentityType IDENTITY_TYPE = IdentityType.ACI;
 
   @Override
@@ -61,10 +59,7 @@ public record AciServiceIdentifier(UUID uuid) implements ServiceIdentifier {
   }
 
   public static AciServiceIdentifier valueOf(final String string) {
-    final boolean valid = !string.startsWith(IDENTITY_TYPE.getStringPrefix());
-    final UUID uuid = UUID.fromString(valid ? string : string.substring(IDENTITY_TYPE.getStringPrefix().length()));
-    Metrics.counter(SERVICE_ID_STRING_COUNTER_NAME, "valid", String.valueOf(valid)).increment();
-    return new AciServiceIdentifier(uuid);
+    return new AciServiceIdentifier(UUID.fromString(string));
   }
 
   public static AciServiceIdentifier fromBytes(final byte[] bytes) {
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifier.java b/service/src/main/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifier.java
index 690b0b81b..341a7f0eb 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifier.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifier.java
@@ -56,6 +56,12 @@ public sealed interface ServiceIdentifier permits AciServiceIdentifier, PniServi
    */
   byte[] toFixedWidthByteArray();
 
+  /**
+   * Parse a service identifier string, which should be a plain UUID string for ACIs and a prefixed UUID string for PNIs
+   *
+   * @param string A service identifier string
+   * @return The parsed {@link ServiceIdentifier}
+   */
   static ServiceIdentifier valueOf(final String string) {
     try {
       return AciServiceIdentifier.valueOf(string);
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifierTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifierTest.java
index 6cefcfe11..4b0d74119 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifierTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/identity/AciServiceIdentifierTest.java
@@ -53,11 +53,12 @@ class AciServiceIdentifierTest {
     final UUID uuid = UUID.randomUUID();
 
     assertEquals(uuid, AciServiceIdentifier.valueOf(uuid.toString()).uuid());
-    assertEquals(uuid, AciServiceIdentifier.valueOf("ACI:" + uuid).uuid());
     assertThrows(IllegalArgumentException.class, () -> AciServiceIdentifier.valueOf("Not a valid UUID"));
     assertThrows(IllegalArgumentException.class, () -> AciServiceIdentifier.valueOf("PNI:" + uuid));
+    assertThrows(IllegalArgumentException.class, () -> AciServiceIdentifier.valueOf("ACI:" + uuid).uuid());
   }
 
+
   @Test
   void fromBytes() {
     final UUID uuid = UUID.randomUUID();
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifierTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifierTest.java
index b06bca9e1..289cb1cbd 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifierTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/identity/ServiceIdentifierTest.java
@@ -32,12 +32,11 @@ class ServiceIdentifierTest {
 
     return Stream.of(
         Arguments.of(uuid.toString(), IdentityType.ACI, uuid),
-        Arguments.of("ACI:" + uuid, IdentityType.ACI, uuid),
         Arguments.of("PNI:" + uuid, IdentityType.PNI, uuid));
   }
 
   @ParameterizedTest
-  @ValueSource(strings = {"Not a valid UUID", "BAD:a9edc243-3e93-45d4-95c6-e3a84cd4a254"})
+  @ValueSource(strings = {"Not a valid UUID", "BAD:a9edc243-3e93-45d4-95c6-e3a84cd4a254", "ACI:a9edc243-3e93-45d4-95c6-e3a84cd4a254"})
   void valueOfIllegalArgument(final String identifierString) {
     assertThrows(IllegalArgumentException.class, () -> ServiceIdentifier.valueOf(identifierString));
   }