diff --git a/pymolfile/molfile/external/CMakeLists.txt b/pymolfile/molfile/external/CMakeLists.txt
index 8c68393ce869bc4d9b0580e0cb5c229fc3213cf7..aca7cc3f01cbc0d7c7ff15053c9e4f78ade359b1 100644
--- a/pymolfile/molfile/external/CMakeLists.txt
+++ b/pymolfile/molfile/external/CMakeLists.txt
@@ -4,7 +4,7 @@ include(ExternalProject)
 
 set(TNG_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/tng")
 set(TNG_INSTALL_DIR "${CMAKE_CURRENT_BINARY_DIR}/tng")
-set(TNG_CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${TNG_INSTALL_DIR} -DBUILD_SHARED_LIBS=OFF)
+set(TNG_CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=${TNG_INSTALL_DIR} -DBUILD_SHARED_LIBS=OFF -DCFLAGS=-fPIC -DCXXFLAGS=-fPIC)
 
 message("TNG_PREFIX='${TNG_PREFIX}'")
 message("TNG_INSTALL_DIR='${TNG_INSTALL_DIR}'")
@@ -16,8 +16,8 @@ ExternalProject_Add(tng
                     GIT_REPOSITORY https://github.com/gromacs/tng.git
 		    GIT_TAG v1.7.6
                     INSTALL_DIR ${TNG_INSTALL_DIR}
-                    CMAKE_ARGS ${TNG_CMAKE_ARGS}
-		    CMAKE_COMMAND CFLAGS=-fPIC CXXFLAGS-fPIC ${CMAKE_COMMAND}
+                    CMAKE_ARGS ${TNG_CMAKE_ARGS} 
+		    CMAKE_COMMAND CFLAGS=-fPIC CXXFLAGS=-fPIC ${CMAKE_COMMAND}
 )