diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 6039ed6..d175483 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -16,7 +16,7 @@ Add_Library                 ( cppmicrohttpd-test-helper STATIC ${SOURCE_FILES} )
 Target_Include_Directories  ( cppmicrohttpd-test-helper
                               PUBLIC
                                 $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/helper>
-                                $<INSTALL_INTERFACE:${cppmicrohttpd_INSTALL_DIR_INCLUDE}> )
+                                $<INSTALL_INTERFACE:${CPPMICROHTTPD_INSTALL_DIR_INCLUDE}> )
 Target_Include_Directories  ( cppmicrohttpd-test-helper
                                 SYSTEM PUBLIC
                                   ${MICROHTTPD_INCLUDE_DIRS} )