diff --git a/interface/CMakeLists.txt b/interface/CMakeLists.txt
index a39283774a..f3cdbf2c22 100644
--- a/interface/CMakeLists.txt
+++ b/interface/CMakeLists.txt
@@ -77,7 +77,7 @@ endif (WIN32)
 foreach(EXTERNAL_SOURCE_SUBDIR ${EXTERNAL_SOURCE_SUBDIRS})
   file(GLOB_RECURSE SUBDIR_SRCS external/${EXTERNAL_SOURCE_SUBDIR}/src/*.cpp external/${EXTERNAL_SOURCE_SUBDIR}/src/*.c external/${EXTERNAL_SOURCE_SUBDIR}/src/*.h)
   set(INTERFACE_SRCS ${INTERFACE_SRCS} ${SUBDIR_SRCS})
-endforeach(SUBDIR)
+endforeach(EXTERNAL_SOURCE_SUBDIR)
 
 
 find_package(Qt5Core REQUIRED)