diff --git a/src/nwdft/libxc/GNUmakefile b/src/nwdft/libxc/GNUmakefile
index 1d28614f91..9324840c8d 100644
--- a/src/nwdft/libxc/GNUmakefile
+++ b/src/nwdft/libxc/GNUmakefile
@@ -13,10 +13,13 @@ LIBRARY = libnwdft.a
 LIB_INCLUDES = -I../include 
 ifdef USE_LIBXC
 LIB_DEFINES += -DXC_MAJOR_VERSION=$(shell grep XC_MAJOR_VERSION ../../libext/libxc/install/include/xc_version.h |cut -d " " -f 3)
+LIB_DEFINES += -DLIBXC_NP_SIZE=$(shell ./libxc_findsizenp.sh ../../libext/libxc/install/include)
 LIB_INCLUDES += -I../../libext/libxc/install/include
 endif
 ifdef LIBXC_INCLUDE
-LIB_DEFINES += -DXC_MAJOR_VERSION=$(shell grep XC_MAJOR_VERSION $(LIBXC_INCLUDE)/xc_version.h |cut -d " " -f 3)
+LIB_DEFINES += -DXC_MAJOR_VERSION=$(shell grep XC_MAJOR_VE
+RSION $(LIBXC_INCLUDE)/xc_version.h |cut -d " " -f 3)
+LIB_DEFINES += -DLIBXC_NP_SIZE=$(shell ./libxc_findsizenp.sh $(LIBXC_INCLUDE))
 LIB_INCLUDES += -I$(LIBXC_INCLUDE)
 endif
 LIB_INCLUDES += -I.
diff --git a/src/nwdft/libxc/libxc_findsizenp.sh b/src/nwdft/libxc/libxc_findsizenp.sh
new file mode 100755
index 0000000000..185d296148
--- /dev/null
+++ b/src/nwdft/libxc/libxc_findsizenp.sh
@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+npstring=$(egrep np "$1"/xc.h|head -1)
+np_array=($npstring)
+count=-1
+sizenp_string=' '
+for substring in "${np_array[@]}"; do
+    [[ $substring == "np," ]] && sizenp_string=${np_array[$count]} && break
+    ((++count))
+done
+if [[ "$sizenp_string" == 'int' ]]; then
+    size_np=4	       	       
+elif [[ "$sizenp_string" == 'size_t' ]]; then
+    size_np=8
+else
+    echo "unexpected sizenp_string $sizenp_string"
+    exit 1
+fi
+echo $size_np
diff --git a/src/nwdft/libxc/nwchem_libxc_compute.F b/src/nwdft/libxc/nwchem_libxc_compute.F
index f7ac9abe65..0db19ba582 100644
--- a/src/nwdft/libxc/nwchem_libxc_compute.F
+++ b/src/nwdft/libxc/nwchem_libxc_compute.F
@@ -63,10 +63,12 @@
       logical gga,mgga,dolap
       logical,external :: nwchem_libxc_family
 
-#if XC_MAJOR_VERSION > 5
+#if LIBXC_NP_SIZE == 4
+      integer*4 nqs
+#elif LIBXC_NP_SIZE == 8
       integer(c_size_t) :: nqs
-#else
-      integer*4 :: nqs
+#elif
+#error "unexpected value for LIBXC_NP_SIZE"
 #endif
 #ifdef USE_LIBXC      
       type(xc_f03_func_t) :: xcfunc