diff --git a/winbuild/MakefileBuild.vc b/winbuild/MakefileBuild.vc
index 8d68b3184..5cc16501b 100644
--- a/winbuild/MakefileBuild.vc
+++ b/winbuild/MakefileBuild.vc
@@ -393,11 +393,11 @@ CFGSET = true
 !IF "$(DEBUG)"=="yes"
 RC_FLAGS = /dDEBUGBUILD=1 /Fo $@ $(LIBCURL_SRC_DIR)\libcurl.rc
 CURL_CC       = $(CC_DEBUG) $(RTLIB_DEBUG)
-CURL_RC_FLAGS = /i../include /dDEBUGBUILD=1 /Fo $@ $(CURL_SRC_DIR)\curl.rc
+CURL_RC_FLAGS = $(CURL_RC_FLAGS) /i../include /dDEBUGBUILD=1 /Fo $@ $(CURL_SRC_DIR)\curl.rc
 !ELSE
 RC_FLAGS = /dDEBUGBUILD=0 /Fo $@ $(LIBCURL_SRC_DIR)\libcurl.rc
 CURL_CC       = $(CC_NODEBUG) $(RTLIB)
-CURL_RC_FLAGS = /i../include /dDEBUGBUILD=0 /Fo $@ $(CURL_SRC_DIR)\curl.rc
+CURL_RC_FLAGS = $(CURL_RC_FLAGS) /i../include /dDEBUGBUILD=0 /Fo $@ $(CURL_SRC_DIR)\curl.rc
 !ENDIF
 
 !IF "$(AS_DLL)" == "true"