diff --git a/CMakeLists.txt b/CMakeLists.txt
index 744af78f803ca04af0b1a907674e70fbbef25c70..ee0c4a3b8150baf39844f6849f5ee8e2862b9783 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,7 +9,7 @@ set(CMAKE_C_STANDARD 11)
 
 add_definitions ("-D_GNU_SOURCE")
 
-if(NOT ${SUBMODULES_NO_BUILD} MATCHES ON)
+if(NOT (${SUBMODULES_NO_BUILD} MATCHES ON))
     add_subdirectory(libdap)
 endif()