diff --git a/gstlal-calibration/tests/check_calibration/ASD_plots b/gstlal-calibration/tests/check_calibration/ASD_plots
index a9abc8497b98381189f29d8ff746dde1055c4044..558e0a13223e5791d74353272c35a3147b8606d5 100755
--- a/gstlal-calibration/tests/check_calibration/ASD_plots
+++ b/gstlal-calibration/tests/check_calibration/ASD_plots
@@ -23,7 +23,7 @@ parser.add_option("--analyze-additional-hoft-channel", action="store_true", help
 parser.add_option("--additional-hoft-channel-name", metavar = "name", default = "DCS-CALIB_STRAIN", help = "Channel name for additional h(t) channel frames. (Default = DCS-CALIB_STRAIN)")
 parser.add_option("--additional-hoft-frame-cache", metavar = "name", help = "additional h(t) frame cache file.")
 parser.add_option("--calcs-channel-name", metavar = "name", default = "CAL-DELTAL_EXTERNAL_DQ", help = "Channel name for h(t) channel in raw frames. (Default = CAL-DELTAL_EXTERNAL_DQ)")
-parser.add_option("--filename-suffix", type = str, default = None, help = "Suffix to add to the end of filenames")
+parser.add_option("--filename-suffix", type = str, default = "", help = "Suffix to add to the end of filenames")
 
 options, filenames = parser.parse_args()
 
diff --git a/gstlal-calibration/tests/check_calibration/latency_plot.py b/gstlal-calibration/tests/check_calibration/latency_plot.py
index ad971a87b4f85521432bffdf712d9265ddbe74c5..4f1f3753da2667cd0212321608aeedb2c6236afb 100644
--- a/gstlal-calibration/tests/check_calibration/latency_plot.py
+++ b/gstlal-calibration/tests/check_calibration/latency_plot.py
@@ -14,7 +14,7 @@ parser = OptionParser()
 parser.add_option("--intime-file", metavar = "file", type = str, help = "File that contains data timestamps and real time of input data")
 parser.add_option("--outtime-file", metavar = "file", type = str, help = "File that contains data timestamps and real time of output data")
 parser.add_option("--plot-title", metavar = "name", type = str, help = "Title of the plot")
-parser.add_option("--plot-filename-prefix", metavar = "file", type = str, help = "Start of the name of the file containing the plot. GPS start time, duration of plot, and .pdf are added")
+parser.add_option("--plot-filename-prefix", metavar = "file", type = str, default = "", help = "Start of the name of the file containing the plot. GPS start time, duration of plot, and .pdf are added")
 
 options, filenames = parser.parse_args()
 
diff --git a/gstlal-calibration/tests/check_calibration/pcal2darm_timeseries.py b/gstlal-calibration/tests/check_calibration/pcal2darm_timeseries.py
index fd9c77ee42affb8b4561c32fd44fb90cdec39451..7404c48204d82205c3349997ebd3ceb3ec244a27 100644
--- a/gstlal-calibration/tests/check_calibration/pcal2darm_timeseries.py
+++ b/gstlal-calibration/tests/check_calibration/pcal2darm_timeseries.py
@@ -82,7 +82,7 @@ parser.add_option("--demodulation-time", metavar = "seconds", type = int, defaul
 parser.add_option("--magnitude-ranges", metavar = "list", type = str, default = "0.9,1.1;0.9,1.1;0.9,1.1", help = "Ranges for magnitude plots. Semicolons separate ranges for different plots, and commas separate min and max values.")
 parser.add_option("--phase-ranges", metavar = "list", type = str, default = "-6.0,6.0;-6.0,6.0;-6.0,6.0", help = "Ranges for phase plots, in degrees. Semicolons separate ranges for different plots, and commas separate min and max values.")
 parser.add_option("--labels", metavar = "list", type = str, help = "Comma-separated List of labels for each calibrated channel being tested. This is put in the plot legends and in the txt file names to distinguish them.")
-parser.add_option("--file-name-suffix", metavar = "name", type = str, default = None, help = "Suffix for naming unique file.")
+parser.add_option("--file-name-suffix", metavar = "name", type = str, default = "", help = "Suffix for naming unique file.")
 
 options, filenames = parser.parse_args()
 
diff --git a/gstlal-calibration/tests/check_calibration/plot_transfer_function.py b/gstlal-calibration/tests/check_calibration/plot_transfer_function.py
index 707f9ae07a09e187531c52ba1ae9dc6eccaf805c..30a9c68342b25249898e35f60e5a559a3d46619e 100644
--- a/gstlal-calibration/tests/check_calibration/plot_transfer_function.py
+++ b/gstlal-calibration/tests/check_calibration/plot_transfer_function.py
@@ -95,7 +95,7 @@ parser.add_option("--magnitude-max", type = float, default = 1.1, help = "Maximu
 parser.add_option("--phase-min", metavar = "degrees", type = float, default = -6, help = "Minimum for phase plot, in degrees")
 parser.add_option("--phase-max", metavar = "degrees", type = float, default = 6, help = "Maximum for phase plot, in degrees")
 parser.add_option("--labels", metavar = "list", type = str, default = None, help = "Comma-separated list of labels corresponding to each transfer function, to be added to plot legend and txt file names.")
-parser.add_option("--filename-suffix", type = str, default = None, help = "Suffix for filename to make it unique.")
+parser.add_option("--filename-suffix", type = str, default = "", help = "Suffix for filename to make it unique.")
 
 options, filenames = parser.parse_args()