diff --git a/metplus/wrappers/command_builder.py b/metplus/wrappers/command_builder.py
index e41b51cf8c..4148725b14 100755
--- a/metplus/wrappers/command_builder.py
+++ b/metplus/wrappers/command_builder.py
@@ -968,6 +968,9 @@ def find_and_check_output_file(self, time_info=None,
         # replace wildcard character * with all
         output_path = output_path.replace('*', 'all')
 
+        # replace any whitespace with an underscore
+        output_path = '_'.join(output_path.split())
+
         skip_if_output_exists = self.c_dict.get('SKIP_IF_OUTPUT_EXISTS', False)
 
         # get directory that the output file will exist