diff --git a/src/zombiereloaded.sp b/src/zombiereloaded.sp
index e526886..d0becc7 100644
--- a/src/zombiereloaded.sp
+++ b/src/zombiereloaded.sp
@@ -26,6 +26,7 @@
 #include "zr/log"
 #include "zr/cvars"
 #include "zr/config"
+#include "zr/serial"
 #include "zr/translation"
 #include "zr/sayhooks"
 #include "zr/tools"
@@ -169,6 +170,7 @@ public OnLibraryAdded(const String:name[])
 public OnMapStart()
 {
     // Forward event to modules.
+    SerialOnMapStart();
     RoundEndOnMapStart();
     InfectOnMapStart();
     SEffectsOnMapStart();
diff --git a/src/zr/serial.inc b/src/zr/serial.inc
new file mode 100644
index 0000000..9e347ef
--- /dev/null
+++ b/src/zr/serial.inc
@@ -0,0 +1,85 @@
+/*
+ * ============================================================================
+ *
+ *   Zombie:Reloaded
+ *
+ *   File:          serial.inc
+ *   Type:          Core
+ *   Description:   Client serial number tracking API.
+ *
+ * ============================================================================
+ */
+
+/**
+ * Maximum length of a client's serial number.
+ */
+#define SERIAL_MAX_LENGTH 8
+
+/**
+ * Array to store client serial numbers.
+ */
+new Handle:arraySerial = INVALID_HANDLE;
+
+/**
+ * Map is starting.
+*/
+SerialOnMapStart()
+{
+    // If array exists, destroy before recreating.
+    if (arraySerial != INVALID_HANDLE)
+    {
+        CloseHandle(arraySerial);
+    }
+    
+    // Create array.
+    arraySerial = CreateArray();
+}
+
+/**
+ * Add client serial number to global array.
+ * 
+ * @param client    The client index.
+ * @return          True if the client was added successfully, false if the client already exists.
+ */
+bool:SerialAddClient(client)
+{
+    // Check if client is already added.
+    new bool:exists = SerialClientExists(client);
+    if (exists)
+    {
+        return false;
+    }
+    
+    // Get client's serial number.
+    new serial = GetClientSerial(client);
+    
+    // Push serial number into the global array.
+    PushArrayCell(arraySerial, serial);
+    
+    // Client added successfully.
+    return true;
+}
+
+/**
+ * Check if a client has been added to the global array.
+ * 
+ * @param client    The client index.
+ * @return          True if the client exists, false otherwise.
+ */
+bool:SerialClientExists(client)
+{
+    // Get client's serial number.
+    new serial = GetClientSerial(client);
+    
+    // Return true if value was found, false otherwise.
+    return (FindValueInArray(arraySerial, serial) != -1);
+}
+
+/**
+ * Reset serial number array.
+ */
+SerialReset()
+{
+    // Clear array.
+    ClearArray(arraySerial);
+}
\ No newline at end of file
diff --git a/src/zr/zspawn.inc b/src/zr/zspawn.inc
index a3e2e46..0d13abd 100644
--- a/src/zr/zspawn.inc
+++ b/src/zr/zspawn.inc
@@ -15,11 +15,6 @@
  */
 new Handle:tZSpawn = INVALID_HANDLE;
 
-/**
- * Array to block zspawn for a unique client serial number.
- */
-new bool:g_bZSpawnBlock[MAXPLAYERS + 1];
-
 /**
  * Map is starting.
  */
@@ -42,11 +37,8 @@ ZSpawnOnClientDisconnect(client)
         return;
     }
     
-    // Get client's unique serial number.
-    new serial = GetClientSerial(client);
-    
-    // Block zspawn.
-    g_bZSpawnBlock[serial] = true;
+    // Add client serial to global array.
+    SerialAddClient(client);
 }
 
 /**
@@ -56,11 +48,8 @@ ZSpawnOnClientDisconnect(client)
  */
 ZSpawnOnClientDeath(client)
 {
-    // Get client's unique serial number.
-    new serial = GetClientSerial(client);
-    
-    // Block zspawn.
-    g_bZSpawnBlock[serial] = true;
+    // Add client serial to global array.
+    SerialAddClient(client);
 }
 
 /**
@@ -68,13 +57,8 @@ ZSpawnOnClientDeath(client)
  */
 ZSpawnOnRoundStart()
 {
-    // Disable flag that blocks zspawn for all clients.
-    // x = client index.
-    for (new x = 1; x <= MaxClients; x++)
-    {
-        // Unblock zspawn.
-        g_bZSpawnBlock[x] = false;
-    }
+    // Reset serial number array.
+    SerialReset();
     
     // If zspawn timer is running, then kill it.
     if (tZSpawn != INVALID_HANDLE)
@@ -169,8 +153,7 @@ bool:ZSpawnClient(client)
     }
     
     // Block if client has already played during this round.
-    new serial = GetClientSerial(client);
-    if (g_bZSpawnBlock[serial])
+    if (SerialClientExists(client))
     {
         // Tell client the command may only be used when joining late.
         ZR_PrintToChat(client, "ZSpawn double spawn");