diff --git a/CMakeLists.txt b/CMakeLists.txt
index f1390049..d6a11e67 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -134,11 +134,11 @@ if (USE_TLS)
     elseif (USE_SECURE_TRANSPORT)
         list( APPEND IXWEBSOCKET_HEADERS ixwebsocket/IXSocketAppleSSL.h)
         list( APPEND IXWEBSOCKET_SOURCES ixwebsocket/IXSocketAppleSSL.cpp)
-    else (USE_OPEN_SSL)
+    elseif (USE_OPEN_SSL)
         list( APPEND IXWEBSOCKET_HEADERS ixwebsocket/IXSocketOpenSSL.h)
         list( APPEND IXWEBSOCKET_SOURCES ixwebsocket/IXSocketOpenSSL.cpp)
     else()
-        message(STATUS "TLS Configuration error: unknown backend")
+        message(FATAL_ERROR "TLS Configuration error: unknown backend")
     endif()
 endif()
 
@@ -156,7 +156,7 @@ if (USE_TLS)
     elseif (USE_SECURE_TRANSPORT)
         target_compile_definitions(ixwebsocket PUBLIC IXWEBSOCKET_USE_SECURE_TRANSPORT)
     else()
-        message(STATUS "TLS Configuration error: unknown backend")
+        message(FATAL_ERROR "TLS Configuration error: unknown backend")
     endif()
 endif()