diff --git a/CMakeLists.txt b/CMakeLists.txt
index 42f0d2649..fdddc4fc2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -186,7 +186,7 @@ IF (NOT INSTALL_LAYOUT)
 ELSE ()
     # Remove visibility flag for now as it breaks Ubuntu 18.05 and we need to
     # fix our libraries anyway
-    STRING(REPLACE "-fvisibility=hidden" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+    STRING(REPLACE "-fvisibility=hidden" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
     # TODO: Re-enable these and fix the warnings they generate
     MY_CHECK_AND_SET_COMPILER_FLAG("-Wno-ignored-qualifiers -Wno-overloaded-virtual -Wno-vla -Wno-non-virtual-dtor -Wno-extra -D_DEBUG" DEBUG)
 ENDIF()