diff --git a/regtest/adjmat/rt-dfg-wcsurf/plumed.dat b/regtest/adjmat/rt-dfg-wcsurf/plumed.dat
index 0a49f34ea8079280bb1fefd64cad29d38d0e0d26..37f124bc53f8d4ba09271241e955fcacb06e7175 100644
--- a/regtest/adjmat/rt-dfg-wcsurf/plumed.dat
+++ b/regtest/adjmat/rt-dfg-wcsurf/plumed.dat
@@ -5,7 +5,7 @@ cf: MFILTER_MORE DATA=c1 SWITCH={RATIONAL D_0=2.0 R_0=0.1} LOWMEM
 # Build a contact matrix
 mat: CONTACT_MATRIX ATOMS=cf SWITCH={EXP D_0=4.0 R_0=0.5 D_MAX=6.0} 
 # Find largest cluster
-dfs: DFSCLUSTERING MATRIX=mat
+dfs: DFSCLUSTERING MATRIX=mat LOWMEM
 clust1: CLUSTER_PROPERTIES CLUSTERS=dfs CLUSTER=1 
 nat: CLUSTER_NATOMS CLUSTERS=dfs CLUSTER=1