diff --git a/juce_amalgamated.cpp b/juce_amalgamated.cpp
index f4d6c25d32..4d12f6ad76 100644
--- a/juce_amalgamated.cpp
+++ b/juce_amalgamated.cpp
@@ -16336,7 +16336,7 @@ bool JUCEApplication::initialiseApp (String& commandLine)
 
     initialiseJuce_GUI();
 
-    InterProcessLock* appLock = 0;
+    jassert (appLock == 0); // initialiseApp must only be called once!
 
     if (! moreThanOneInstanceAllowed())
     {
diff --git a/src/application/juce_Application.cpp b/src/application/juce_Application.cpp
index d8dc039cbf..b22a0b6af2 100644
--- a/src/application/juce_Application.cpp
+++ b/src/application/juce_Application.cpp
@@ -194,7 +194,7 @@ bool JUCEApplication::initialiseApp (String& commandLine)
 
     initialiseJuce_GUI();
 
-    InterProcessLock* appLock = 0;
+    jassert (appLock == 0); // initialiseApp must only be called once!
 
     if (! moreThanOneInstanceAllowed())
     {