diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -431,6 +431,7 @@
     message("!! you MUST explicity define CMAKE_INSTALL_PREFIX !!")
     message("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
     message("${ESCAPE}[0m")
+    message(FATAL_ERROR "Aborting")
   endif(QCA_INSTALL_IN_QT_PREFIX)
 
   message("")