diff --git a/regtest/basic/rt13-lepton/COLVAR.reference b/regtest/basic/rt13-lepton/COLVAR.reference
new file mode 100644
index 0000000000000000000000000000000000000000..972e0086bc96eb193224cdc19559802ac61feefd
--- /dev/null
+++ b/regtest/basic/rt13-lepton/COLVAR.reference
@@ -0,0 +1,12 @@
+#! FIELDS time t1 t2 t3 cc1 cc2 cc3 all
+#! SET min_t1 -pi
+#! SET max_t1 pi
+#! SET min_t2 -pi
+#! SET max_t2 pi
+#! SET min_t3 -pi
+#! SET max_t3 pi
+ 0.000000 -1.69727 -1.69727 0.25617 2.18345 0.00000 5.76145 0.80109
+ 0.050000 -1.81921 -1.81921 0.29414 2.49031 0.00000 6.61905 0.96085
+ 0.100000 -1.92318 -1.92318 0.32805 2.77543 0.00000 7.39721 1.10906
+ 0.150000 -2.02490 -2.02490 0.36930 3.07533 0.00000 8.20048 1.26588
+ 0.200000 -2.11789 -2.11789 0.41443 3.36757 0.00000 8.97091 1.41952
diff --git a/regtest/basic/rt13-lepton/Makefile b/regtest/basic/rt13-lepton/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..3703b27cea227aa053fb6d1d73f861e4384dbcee
--- /dev/null
+++ b/regtest/basic/rt13-lepton/Makefile
@@ -0,0 +1 @@
+include ../../scripts/test.make
diff --git a/regtest/basic/rt13-lepton/config b/regtest/basic/rt13-lepton/config
new file mode 100644
index 0000000000000000000000000000000000000000..55737833d20ab1d0fe8b05989286697ae3bf298d
--- /dev/null
+++ b/regtest/basic/rt13-lepton/config
@@ -0,0 +1,6 @@
+type=driver
+# this is to test a different name
+arg="--plumed plumed.dat --trajectory-stride 10 --timestep 0.005 --ixyz trajectory.xyz --dump-forces forces --dump-forces-fmt=%10.6f"
+extra_files="../../trajectories/trajectory.xyz"
+# this tells plumed to use lepton as a matheval replacement:
+export PLUMED_USE_LEPTON=yes
diff --git a/regtest/basic/rt13-lepton/forces.reference b/regtest/basic/rt13-lepton/forces.reference
new file mode 100644
index 0000000000000000000000000000000000000000..19b9914bf2eeb1c7461064a62a4a2db9688c4c41
--- /dev/null
+++ b/regtest/basic/rt13-lepton/forces.reference
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+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
+X 0.000000 0.000000 0.000000
diff --git a/regtest/basic/rt13-lepton/plumed.dat b/regtest/basic/rt13-lepton/plumed.dat
new file mode 100644
index 0000000000000000000000000000000000000000..99f6ece69bb250dbb911947d801e2ae77c7b1cf5
--- /dev/null
+++ b/regtest/basic/rt13-lepton/plumed.dat
@@ -0,0 +1,23 @@
+g1: GROUP ATOMS=1-10
+c1: CENTER ATOMS=g1
+
+t1: TORSION ATOMS=1,6,10,15
+t2: TORSION VECTOR1=6,1 AXIS=6,10 VECTOR2=10,15
+t3: TORSION VECTOR1=6,1 AXIS=20,7 VECTOR2=10,c1
+
+cc1: MATHEVAL ARG=t1,t2,t3 FUNC=x^2+y+0*z+1 PERIODIC=NO
+cc2: MATHEVAL ARG=t1,t2,t3 FUNC=0*x^3+0*y^3+0*z^3 PERIODIC=NO
+cc3: MATHEVAL ARG=t1,t2 FUNC=x^2+y^2 PERIODIC=NO
+
+all: MATHEVAL ARG=t1,t2,t3,cc1,cc2,cc3 VAR=a1,a2,a3,a4,a5,a6 FUNC={ (a1+a2+a3+a4+a5+a6) / 6.0 } PERIODIC=NO
+
+RESTRAINT ARG=all AT=0 SLOPE=1.0
+
+PRINT ...
+ STRIDE=2
+ ARG=t1,t2,t3,cc1,cc2,cc3,all
+ FILE=COLVAR FMT=%6.5f
+... PRINT
+
+ENDPLUMED
+