diff --git a/debian/changelog b/debian/changelog
index 802fa95616d..dcfe769bc26 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -2,6 +2,7 @@
   * Added additional magnitude-scaling relationships to thingbaijam2017.py
 
   [Michele Simionato]
+  * Added checks on MAX_NUM_RUPTURES and ps_grid_spacing
   * Added command `oq info db` to extract the path to the sqlite file
   * Implemented a workflow to run the 2026 Global Risk Model
 
diff --git a/openquake/calculators/preclassical.py b/openquake/calculators/preclassical.py
index da27c129788..86b7723c54b 100644
--- a/openquake/calculators/preclassical.py
+++ b/openquake/calculators/preclassical.py
@@ -35,7 +35,7 @@
 from openquake.commonlib import readinput
 from openquake.calculators import base
 
-MAX_NUM_RUPTURES = 20_000  # only on fault sources
+MAX_NUM_RUPTURES = 20_000  # tentative
 U16 = numpy.uint16
 U32 = numpy.uint32
 F32 = numpy.float32
@@ -94,12 +94,13 @@ def collapse_nphc(src):
         src.magnitude_scaling_relationship = PointMSR()
 
 
-def _filter_mag(srcs, min_mag):
+def _filter_mag(srcs, min_mag, strict):
     # filter by magnitude and count the ruptures
     mmag = getdefault(min_mag, srcs[0].tectonic_region_type)
     out = [src for src in srcs if src.get_mags()[-1] >= mmag]
     for ss in out:
-        if ss.num_ruptures > MAX_NUM_RUPTURES and ss.code in b'FSCXKN':
+        if ss.num_ruptures > MAX_NUM_RUPTURES and strict and not hasattr(
+                ss, 'location'):  # same condition as in `get_ctxs`
             raise RuntimeError('%s has too many ruptures' % ss)
     return out
 
@@ -109,6 +110,7 @@ def filter_weight(srcs, sf, cmaker, secparams, monitor):
     Filter and weight the sources. Also split them, except for
     pointlike and multifault sources, which have been split already.
     """
+    oq = cmaker.oq
     mon1 = monitor('building top of ruptures', measuremem=True)
     mon2 = monitor('setting msparams', measuremem=False)
     ry0 = 'ry0' in cmaker.REQUIRES_DISTANCES
@@ -118,7 +120,7 @@ def filter_weight(srcs, sf, cmaker, secparams, monitor):
     splits = []
     for src in srcs:
         if src.code == b'F':
-            if N and N <= cmaker.max_sites_disagg:
+            if N and N <= oq.max_sites_disagg:
                 mask = sf.get_close(secparams) > 0  # shape S
             else:
                 mask = None
@@ -136,14 +138,14 @@ def filter_weight(srcs, sf, cmaker, secparams, monitor):
             src.nsites = 1
         # NB: it is crucial to split only the close sources, for
         # performance reasons (think of Ecuador in SAM)
-        if cmaker.split_sources and src.nsites and src.code != b'F':
+        if oq.split_sources and src.nsites and src.code != b'F':
             # multifault source have been already split in save_and_split
             splits.extend(split_source(src))
         else:
             splits.append(src)
 
     # filter by magnitude and count ruptures
-    splits = _filter_mag(splits, cmaker.oq.minimum_magnitude)
+    splits = _filter_mag(splits, oq.minimum_magnitude, oq.strict)
     if not splits:
         return {}
 
diff --git a/openquake/commonlib/oqvalidation.py b/openquake/commonlib/oqvalidation.py
index b1fdeea8b41..47b462ab4cf 100644
--- a/openquake/commonlib/oqvalidation.py
+++ b/openquake/commonlib/oqvalidation.py
@@ -855,6 +855,11 @@
   Example: *steps_per_interval = 4*.
   Default: 1
 
+strict:
+  Enable strict checking on fault sources and ps_grid_spacing
+  Example: *strict = false*
+  Default: True
+
 tectonic_region_type:
    Used to specify a tectonic region type.
    Example: *tectonic_region_type = Active Shallow Crust*.
@@ -1230,6 +1235,7 @@ class OqParam(valid.ParamSet):
     split_sources = valid.Param(valid.boolean, True)
     split_time = valid.Param(valid.positiveint, None)
     split_by_gsim = valid.Param(valid.positiveint, 0)
+    strict = valid.Param(valid.boolean, True)
     tectonic_region_type = valid.Param(valid.utf8, '*')
     time_event = valid.Param(
         valid.Choice('avg', 'day', 'night', 'transit'), 'avg')
diff --git a/openquake/hazardlib/source_reader.py b/openquake/hazardlib/source_reader.py
index 4bef7db916f..73706fbf79c 100644
--- a/openquake/hazardlib/source_reader.py
+++ b/openquake/hazardlib/source_reader.py
@@ -193,7 +193,7 @@ def save_read_times(dstore, source_models):
 
 def get_csm(oq, full_lt, dstore=None):
     """
-    Build source models from the logic tree and to store
+    Build source models from the logic tree and store
     them inside the `source_full_lt` dataset.
     """
     converter = sourceconverter.SourceConverter(
@@ -235,6 +235,28 @@ def get_csm(oq, full_lt, dstore=None):
         save_read_times(dstore, smdict.values())
     check_duplicates(smdict, strict=oq.disagg_by_src)
 
+    # checking ps_grid_spacing
+    pointlike_sources = 0
+    for sm in smdict.values():
+        for sg in sm.src_groups:
+            for src in sg:
+                if src.code in b'PAM':
+                    pointlike_sources += 1
+                    break
+    if (oq.strict and oq.mosaic_model and pointlike_sources and
+        'classical' in oq.calculation_mode and oq.ps_grid_spacing == 0
+        and not oq.sites):
+        raise InvalidFile(f'{oq.inputs["job_ini"]}: '
+                          'missing ps_grid_spacing')
+
+    return build_csm(oq, full_lt, smdict, dstore)
+
+
+def build_csm(oq, full_lt, smdict, dstore):
+    """
+    Applies uncertainties, builds the source groups and returns
+    a CompositeSourceModel instance
+    """
     logging.info('Applying uncertainties')
     groups = _build_groups(full_lt, smdict)
 
diff --git a/openquake/qa_tests_data/event_based_risk/case_4a/jobs.toml b/openquake/qa_tests_data/event_based_risk/case_4a/jobs.toml
index 5de2a393b87..cab4041a419 100644
--- a/openquake/qa_tests_data/event_based_risk/case_4a/jobs.toml
+++ b/openquake/qa_tests_data/event_based_risk/case_4a/jobs.toml
@@ -1,6 +1,6 @@
 [multi.workflow]
 description = "multi-workflow"
-env.OQ_SAMPLE_ASSETS = 0.1
+env.OQ_SAMPLE_ASSETS = 1
 may_fail = ["riskJob"]
 override = {out_file="SES.hdf5", hazard_calculation_id="SES.hdf5"}