diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0a02ef1..a7ebfc1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -31,7 +31,7 @@
 if(PERL_FOUND)
 
     # If NULL Entropy is configured, display an appropriate warning
-    execute_process(COMMAND ${PERL_EXECUTABLE} scripts/config.pl get MBEDTLS_TEST_NULL_ENTROPY
+    execute_process(COMMAND ${PERL_EXECUTABLE} ${CMAKE_SOURCE_DIR}/scripts/config.pl -f ${CMAKE_SOURCE_DIR}/include/mbedtls/config.h get MBEDTLS_TEST_NULL_ENTROPY
                         RESULT_VARIABLE result)
     if(${result} EQUAL 0)
         message(WARNING ${NULL_ENTROPY_WARNING})