diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7ce07851e2..671a204267 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -799,7 +799,7 @@ check_include_files (wctype.h HAVE_WCTYPE_H)
 
 test_big_endian(IS_BIGENDIAN)
 if (IS_BIGENDIAN)
-  set(WORDS_BIGENDIAN)
+  add_compile_definition (WORDS_BIGENDIAN)
 endif()
 
 if (NOT DISABLE_NLS)
diff --git a/libgnucash/engine/gnc-timezone.cpp b/libgnucash/engine/gnc-timezone.cpp
index 6c17e105ea..2040aa52b1 100644
--- a/libgnucash/engine/gnc-timezone.cpp
+++ b/libgnucash/engine/gnc-timezone.cpp
@@ -49,7 +49,7 @@ template<typename T>
 T*
 endian_swap(T* t)
 {
-#if ! WORDS_BIGENDIAN
+#ifndef WORDS_BIGENDIAN
     auto memp = reinterpret_cast<unsigned char*>(t);
     std::reverse(memp, memp + sizeof(T));
 #endif