diff --git a/packaging/win32/install.sh b/packaging/win32/install.sh
index 95635ae5cd..75c602cb9e 100644
--- a/packaging/win32/install.sh
+++ b/packaging/win32/install.sh
@@ -602,7 +602,7 @@ function inst_gnucash() {
 	--prefix=$_GNUCASH_WFSDIR \
 	--enable-debug \
 	CPPFLAGS="${AUTOTOOLS_CPPFLAGS} ${REGEX_CPPFLAGS}" \
-	CFLAGS="${AUTOTOOLS_CPPFLAGS} ${REGEX_CPPFLAGS}" \
+	CFLAGS="${AUTOTOOLS_CPPFLAGS} ${REGEX_CPPFLAGS} -D_WIN32 -DLIBLTDL_DLL_IMPORT" \
 	LDFLAGS="-no-undefined ${AUTOTOOLS_LDFLAGS} ${REGEX_LDFLAGS}" \
 	PKG_CONFIG_PATH="${PKG_CONFIG_PATH}" \
 	PATH="${PATH}"