diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6733ad83a..38ce5f045 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -377,6 +377,9 @@ else ()
   find_package( Backtrace )
   if ( Backtrace_FOUND )
     set ( HAVE_BACKTRACE 1 )
+  else ()
+    set ( Backtrace_LIBRARY "" )
+    set ( Backtrace_HEADER "" )
   endif ()
 endif ()
 check_cxx_source_compiles( "#include <cxxabi.h>