diff --git a/examples/blowout_wake/inputs_SI b/examples/blowout_wake/inputs_SI
index 14eeab4662..e6a9048974 100644
--- a/examples/blowout_wake/inputs_SI
+++ b/examples/blowout_wake/inputs_SI
@@ -11,6 +11,7 @@ max_step = 0
 diagnostic.output_period = 1
 
 hipace.depos_order_xy = 2
+hipace.dt = 1.e-6/clight
 
 boundary.field = Dirichlet
 boundary.particle = Periodic
diff --git a/examples/blowout_wake/inputs_normalized b/examples/blowout_wake/inputs_normalized
index 48da3703d0..4dd47741ee 100644
--- a/examples/blowout_wake/inputs_normalized
+++ b/examples/blowout_wake/inputs_normalized
@@ -7,6 +7,7 @@ amr.max_level = 0
 max_step = 0
 diagnostic.output_period = 1
 
+hipace.dt = 1/clight
 hipace.depos_order_xy = 2
 
 boundary.field = Dirichlet
diff --git a/examples/laser_ionization/inputs_laser_ionization b/examples/laser_ionization/inputs_laser_ionization
index 5f524146f7..41a2761052 100644
--- a/examples/laser_ionization/inputs_laser_ionization
+++ b/examples/laser_ionization/inputs_laser_ionization
@@ -1,5 +1,5 @@
 max_step = 0
-hipace.dt = 0
+hipace.dt = 10.e-6/clight
 hipace.verbose = 3
 
 amr.n_cell = 50 50 50
diff --git a/src/laser/MultiLaser.cpp b/src/laser/MultiLaser.cpp
index 6ac2a28f08..c668b5c385 100644
--- a/src/laser/MultiLaser.cpp
+++ b/src/laser/MultiLaser.cpp
@@ -421,6 +421,8 @@ MultiLaser::AdvanceSlice (const int islice, const Fields& fields, amrex::Real dt
 
     if (!UseLaser(islice)) return;
 
+    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(dt>0, "Cannot use dt=0 or dt<0 with laser");
+
     Hipace::m_num_laser_cells_updated += m_slice_box.d_numPts();
 
     InterpolateChi(fields, geom_field_lev0);
diff --git a/tests/checksum/benchmarks_json/blowout_wake.2Rank.json b/tests/checksum/benchmarks_json/blowout_wake.2Rank.json
index a0a4a1682a..4ee5a3d520 100644
--- a/tests/checksum/benchmarks_json/blowout_wake.2Rank.json
+++ b/tests/checksum/benchmarks_json/blowout_wake.2Rank.json
@@ -1,21 +1,21 @@
 {
   "lev=0": {
-    "Bx": 1090.713964339,
-    "By": 1090.713964339,
-    "Bz": 31.667907950938,
-    "ExmBy": 1647.1039663567,
-    "EypBx": 1647.1039663567,
-    "Ez": 1403.6070905859,
-    "Psi": 2132.3248879604,
-    "Sx": 3061.9838214617,
-    "Sy": 3061.9838214617,
-    "chi": 405683.18832868,
-    "jx": 1077.3968452158,
-    "jx_beam": 0.0,
-    "jy": 1077.3968452158,
-    "jy_beam": 0.0,
+    "Bx": 1090.7154900517,
+    "By": 1090.7154422643,
+    "Bz": 31.667398575322,
+    "ExmBy": 1647.107987011,
+    "EypBx": 1647.1081910522,
+    "Ez": 1403.6094478169,
+    "Psi": 2132.3355039045,
+    "Sx": 3061.986135111,
+    "Sy": 3061.9861100545,
+    "chi": 405683.17903507,
+    "jx": 1077.3961376759,
+    "jx_beam": 9.9270072350142e-11,
+    "jy": 1077.3971049505,
+    "jy_beam": 9.9270070959291e-11,
     "jz_beam": 799.24438903362,
-    "rhomjz": 3938.2517311491
+    "rhomjz": 3938.2515666667
   },
   "beam": {
     "charge": 7448.0,
@@ -24,8 +24,8 @@
     "x": 3871.0,
     "y": 3871.0,
     "z": 21897.12,
-    "ux": 0.0,
-    "uy": 0.0,
+    "ux": 2.3556092993799e-06,
+    "uy": 2.3556093051022e-06,
     "uz": 14896000.0,
     "w": 799.24448893917
   }
diff --git a/tests/checksum/benchmarks_json/reset.2Rank.json b/tests/checksum/benchmarks_json/reset.2Rank.json
index 2eea299f9f..08948994a4 100644
--- a/tests/checksum/benchmarks_json/reset.2Rank.json
+++ b/tests/checksum/benchmarks_json/reset.2Rank.json
@@ -1,21 +1,21 @@
 {
   "lev=0": {
-    "Bx": 1090.6435784789,
-    "By": 1090.6435784789,
-    "Bz": 31.672432358345,
-    "ExmBy": 1646.9810972817,
-    "EypBx": 1646.9810972817,
-    "Ez": 1403.4429508832,
-    "Psi": 2132.0850072334,
-    "Sx": 3061.9089975082,
-    "Sy": 3061.9089975082,
-    "chi": 405683.282164,
-    "jx": 1077.3232567856,
-    "jx_beam": 0.0,
-    "jy": 1077.3232567856,
-    "jy_beam": 0.0,
+    "Bx": 1090.6413080929,
+    "By": 1090.6412063521,
+    "Bz": 31.672811205069,
+    "ExmBy": 1646.9770739969,
+    "EypBx": 1646.9770456234,
+    "Ez": 1403.4313773122,
+    "Psi": 2132.0751054606,
+    "Sx": 3061.9079220281,
+    "Sy": 3061.9078930139,
+    "chi": 405683.28357349,
+    "jx": 1077.3190684908,
+    "jx_beam": 1.9854032540597e-10,
+    "jy": 1077.3188464065,
+    "jy_beam": 1.9854032267884e-10,
     "jz_beam": 799.24438903362,
-    "rhomjz": 3938.1190949076
+    "rhomjz": 3938.1157251251
   },
   "beam": {
     "charge": 7448.0,
@@ -24,9 +24,9 @@
     "x": 3871.0,
     "y": 3871.0,
     "z": 21897.12,
-    "ux": 0.0,
-    "uy": 0.0,
-    "uz": 14896000.0,
+    "ux": 4.7111116218863e-06,
+    "uy": 4.7111115383888e-06,
+    "uz": 14896000.000001,
     "w": 799.24448893917
   }
 }