diff --git a/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Memory.pm b/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Memory.pm
index ff79ac1..601b414 100644
--- a/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Memory.pm
+++ b/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Memory.pm
@@ -214,6 +214,12 @@ sub lock_section {
 
 sub stat { shift->_shared_memory->stat }
 
-sub DESTROY { $_[0]->remove if $_[0]->destroy() }
+sub DESTROY {
+  my $self = shift;
+  if ($self->_shared_memory) {
+    eval { $self->_shared_memory->detach() };
+  }
+  $self->remove if $self->destroy();
+}
 
 !!42;
diff --git a/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Semaphore.pm b/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Semaphore.pm
index 7ca9636..877fd1a 100644
--- a/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Semaphore.pm
+++ b/lib/Mojo/IOLoop/ReadWriteProcess/Shared/Semaphore.pm
@@ -25,14 +25,19 @@ sub _genkey { ftok($0, 0) }
 sub _create {
   my ($self, $key) = @_;
 
-  # Try acquiring already existing semaphore
-  my $sem = IPC::Semaphore->new($key, $self->count, 0);
-  unless (defined $sem) {
+  # Try creating it. IPC_EXCL in flags fails with EEXIST if it already
+  # exists, e.g. from a previous call, or a concurrent process that won the
+  # race to create it - both cases are handled the same way: attach to it.
+  my $sem = IPC::Semaphore->new($key, $self->count, $self->flags);
+  if (defined $sem) {
     warn "[debug:$$] Create semaphore $key" if DEBUG;
-    $sem = IPC::Semaphore->new($key, $self->count, $self->flags);
-    confess 'Semaphore creation failed! ' unless defined($sem);
     $sem->setall($self->_value);
   }
+  else {
+    warn "[debug:$$] Attach to existing semaphore $key" if DEBUG;
+    $sem = IPC::Semaphore->new($key, $self->count, 0);
+  }
+  confess 'Semaphore creation failed! ' unless defined($sem);
   return $sem;
 }
 
diff --git a/t/02_parallel.t b/t/02_parallel.t
index 6f3c52c..b877c1b 100644
--- a/t/02_parallel.t
+++ b/t/02_parallel.t
@@ -70,7 +70,7 @@ subtest batch => sub {
     separate_err => 0,
     set_pipes    => 1
   );
-  $c->start();
+  $c->last->start();
   is $c->last->getline, "Hello world 3\n";
   $c->wait_stop();