diff --git a/objectivec/GPBMessage.m b/objectivec/GPBMessage.m
index 208cfe4e..fdb695ec 100644
--- a/objectivec/GPBMessage.m
+++ b/objectivec/GPBMessage.m
@@ -886,6 +886,7 @@ static GPBUnknownFieldSet *GetOrMakeUnknownFields(GPBMessage *self) {
 - (void)dealloc {
   [self internalClear:NO];
   NSCAssert(!autocreator_, @"Autocreator was not cleared before dealloc.");
+  dispatch_release(readOnlySemaphore_);
   [super dealloc];
 }