diff --git a/lib/blackbox/src/blackbox.rs b/lib/blackbox/src/blackbox.rs
index 031fed63ce..cc8a645eda 100644
--- a/lib/blackbox/src/blackbox.rs
+++ b/lib/blackbox/src/blackbox.rs
@@ -175,6 +175,11 @@ impl Blackbox {
         }
     }
 
+    /// Get the pid stored in session_id.
+    pub(crate) fn session_pid(&self) -> u32 {
+        (self.session_id & 0xffffff) as u32
+    }
+
     pub fn session_id(&self) -> u64 {
         self.session_id
     }
diff --git a/lib/blackbox/src/singleton.rs b/lib/blackbox/src/singleton.rs
index fe31a55392..057d432339 100644
--- a/lib/blackbox/src/singleton.rs
+++ b/lib/blackbox/src/singleton.rs
@@ -36,7 +36,11 @@ pub fn init(mut blackbox: Blackbox) {
             }
         }
     }
-    blackbox.session_id = old_blackbox.session_id;
+
+    // Perserve session_id if pid hasn't been changed.
+    if blackbox.session_pid() == old_blackbox.session_pid() {
+        blackbox.session_id = old_blackbox.session_id;
+    }
 
     *singleton.deref_mut() = blackbox;
 }