diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63c53a8b..65da281d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,8 +76,8 @@ target_compile_definitions(libchibi-common
     BUILDING_DLL=$<AND:$<PLATFORM_ID:Windows>,$<BOOL:${BUILD_SHARED_LIBS}>>
     SEXP_USE_DL=$<BOOL:${BUILD_SHARED_LIBS}>
     SEXP_USE_INTTYPES=$<BOOL:${HAVE_STDINT_H}>
-    SEXP_USE_NTPGETTIME=$<BOOL:HAVE_NTP_GETTIME>
-    SEXP_USE_GREEN_THREADS=$<BOOL:HAVE_POLL_H>
+    SEXP_USE_NTPGETTIME=$<BOOL:${HAVE_NTP_GETTIME}>
+    SEXP_USE_GREEN_THREADS=$<BOOL:${HAVE_POLL_H}>
     SEXP_USE_STRING_STREAMS=$<NOT:$<BOOL:${CYGWIN}>>
     SEXP_USE_BOEHM=$<BOOL:${SEXP_USE_BOEHM}>)