diff --git a/cmake/modules/FindIPOpt.cmake b/cmake/modules/FindIPOpt.cmake
index a9704cf6a19084791364cc7d00bf0cb2785f2ef5..f76866297863d2cdc94e7e6741a8c79b9ebb0e18 100644
--- a/cmake/modules/FindIPOpt.cmake
+++ b/cmake/modules/FindIPOpt.cmake
@@ -29,9 +29,8 @@ find_package_handle_standard_args(Ipopt DEFAULT_MSG IPOPT_INCLUDE_DIR IPOPT_LIBR
 set(HAVE_IPOPT ENABLE_IPOPT)
 
 if(IPOPT_FOUND)
-    set(DUNE_IPOPT_CFLAGS -I${IPOPT_INCLUDE_DIR})
-    set_property(GLOBAL APPEND PROPERTY ALL_PKG_FLAGS "-DENABLE_IPOPT")
-    set_property(GLOBAL APPEND PROPERTY ALL_PKG_FLAGS ${DUNE_IPOPT_CFLAGS})
+    set(DUNE_IPOPT_CFLAGS "-I${IPOPT_INCLUDE_DIR} -DENABLE_IPOPT=1")
+    set_property(GLOBAL APPEND PROPERTY ALL_PKG_FLAGS "-I${IPOPT_INCLUDE_DIR}")
     set(IPOPT_LIBRARY ${IPOPT_LIBRARY})
     if (HSL_FOUND)
         set (IPOPT_LIBRARY ${HSL_LIBRARY} ${IPOPT_LIBRARY})