diff --git a/imsim/lsst_image.py b/imsim/lsst_image.py
index 8b6a4329..302ec1bf 100644
--- a/imsim/lsst_image.py
+++ b/imsim/lsst_image.py
@@ -38,7 +38,14 @@ def setup(self, config, base, image_num, obj_num, ignore, logger):
                      image_num,image_num,obj_num)
 
         self.nobjects = self.getNObj(config, base, image_num, logger=logger)
-        logger.debug('image %d: nobj = %d',image_num,self.nobjects)
+        if 'nobjects' in config:
+            # User specified nobjects.
+            # Make sure it's not more than what any input catalog can
+            # handle (we don't want repeated objects).
+            input_nobj = galsim.config.ProcessInputNObjects(base)
+            if input_nobj is not None:
+                self.nobjects = min(self.nobjects, input_nobj)
+        logger.info('image %d: nobj = %d', image_num, self.nobjects)
 
         # These are allowed for LSST_Image, but we don't use them here.
         extra_ignore = [ 'image_pos', 'world_pos', 'stamp_size', 'stamp_xsize', 'stamp_ysize',
diff --git a/tests/test_lsst_image.py b/tests/test_lsst_image.py
new file mode 100644
index 00000000..6eb566a9
--- /dev/null
+++ b/tests/test_lsst_image.py
@@ -0,0 +1,71 @@
+import os
+import shutil
+import sys
+import logging
+from pathlib import Path
+import numpy as np
+import galsim
+
+
+def test_image_nobjects():
+    """
+    Test that the minimum of the optional config setting of
+    image.nobjects and the number of objects available is used to
+    avoid repeated object renderings.
+    """
+    imsim_dir = os.path.dirname(os.path.abspath(str(Path(__file__).parent)))
+    os.environ['SIMS_SED_LIBRARY_DIR'] \
+        = os.path.join(imsim_dir, 'tests', 'data', 'test_sed_library')
+    template = os.path.join(imsim_dir, 'config', 'imsim-config-instcat.yaml')
+    instcat_file = os.path.join(imsim_dir, 'tests', 'data',
+                                'test_multiproc_instcat.txt')
+
+    logger = logging.getLogger('test_lsst_image')
+    if len(logger.handlers) == 0:
+        logger.addHandler(logging.StreamHandler(sys.stdout))
+        logger.setLevel(logging.CRITICAL)  # silence the log messages
+
+    camera = "LsstCam"
+    output_dir = f"fits_{camera}"
+
+    # Loop over values of image.nobjects that bracket the expected number
+    # from the instance catalog to test the number of objects actually
+    # rendered.
+    for nobjects, nexpected in zip((1, 5, ""), (1, 3, 3)):
+        config = {'modules': ['imsim'],
+                  'template': template,
+                  'input.instance_catalog.file_name': instcat_file,
+                  'input.opsim_data.file_name': instcat_file,
+                  'input.tree_rings': '',
+                  'input.atm_psf': '',
+                  'input.checkpoint': '',
+                  'image.sky_level': 0,
+                  'image.random_seed': 42,
+                  'image.sensor': '',
+                  'image.nobjects': nobjects,
+                  'stamp.fft_sb_thresh': '1e5',
+                  'stamp.size': 48,
+                  'psf.items': '',
+                  'psf.type': 'Gaussian',
+                  'psf.fwhm': 0.7,
+                  'output.camera': camera,
+                  'output.cosmic_ray_rate': 0,
+                  'output.det_num.first': 94,
+                  'output.nfiles': 1,
+                  'output.readout': '',
+                  'output.dir': output_dir,
+                  'output.truth.dir': output_dir,
+                  'output.truth.file_name.format': 'centroid_%08d-%1d-%s-%s-det%03d.txt',
+        }
+
+        galsim.config.Process(config, logger=logger)
+        data = np.genfromtxt(f"{output_dir}/centroid_00161899-0-r-R22_S11-det094.txt",
+                             names=True)
+        assert nexpected == data.size
+
+        shutil.rmtree(output_dir)
+
+if __name__ == '__main__':
+    testfns = [v for k, v in vars().items() if k[:5] == 'test_' and callable(v)]
+    for testfn in testfns:
+        testfn()