diff --git a/CMakeLists.txt b/CMakeLists.txt
index e0aacaa17..df074b0c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -292,10 +292,11 @@ if( IEEE_LE )
     set( IEEE_BE 0 )
 endif()
 
+set( ECCODES_ON_WINDOWS 0 )
 if( EC_OS_NAME MATCHES "windows" )
     # Symbols need to be explicitly exported on Windows so we can link to dlls.
     set( CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE )
-    set( ECCODES_ON_WINDOWS TRUE )
+    set( ECCODES_ON_WINDOWS 1 )
 
     # Suppress compliler warnings - see ECC-850
     # Suppress warnings about using 'insecure' functions. Fixing this would require changes all over
diff --git a/tests/include.ctest.sh.in b/tests/include.ctest.sh.in
index 81ef455c8..148c92e39 100644
--- a/tests/include.ctest.sh.in
+++ b/tests/include.ctest.sh.in
@@ -40,5 +40,6 @@ HAVE_PNG=@HAVE_PNG@
 HAVE_AEC=@HAVE_AEC@
 HAVE_EXTRA_TESTS=@HAVE_EXTRA_TESTS@
 HAVE_MEMFS=@HAVE_MEMFS@
+ECCODES_ON_WINDOWS=@ECCODES_ON_WINDOWS@
 
 echo "Current directory: `pwd`"