diff --git a/MVMCore/MVMCore/Models/ActionType/Client Parameters/ClientParameterHandler.swift b/MVMCore/MVMCore/Models/ActionType/Client Parameters/ClientParameterHandler.swift
index fe420ef..2d59771 100644
--- a/MVMCore/MVMCore/Models/ActionType/Client Parameters/ClientParameterHandler.swift	
+++ b/MVMCore/MVMCore/Models/ActionType/Client Parameters/ClientParameterHandler.swift	
@@ -88,19 +88,24 @@
                     complete = true
                 }
             }
-
+            
             // Setup timeout.
             self.parametersWorkQueue.asyncAfter(deadline: .now() + .seconds(Int(timeout)), execute: timeoutWorkItem)
-
+            
             // Setup the parameter execution.
             for (index, parameterHandler) in self.parameterHandlerList.enumerated() {
+                let parameterType = parameterHandler.clientParameterModel.type
                 self.group.enter()
                 parameterHandler.fetchClientParameters(requestParameters: requestParameters,
                                                        timingOutIn: timeout) { (receivedParameter) in
                     // Queue the results for merge.
                     self.parametersWorkQueue.async {
-                        returnedList[index] = receivedParameter
-                        self.group.leave() // Leaving is only done after setup (barriered).
+                        if (returnedList[index] != nil) {
+                            MVMCoreLoggingHandler.shared()?.addError(toLog: MVMCoreErrorObject(title: nil, message: "Client parameter \(parameterType) has already executed. The completion handler should only be called once!", code: ErrorCode.default.rawValue, domain: ErrorDomainNative, location: String(describing: ClientParameterHandler.self))!)
+                        } else  {
+                            returnedList[index] = receivedParameter
+                            self.group.leave() // Leaving is only done after setup (barriered).
+                        }
                     }
                 }
             }