diff --git a/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersister.py b/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersister.py
index 8fd8b910634..4dcc1b5d98e 100644
--- a/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersister.py
+++ b/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersister.py
@@ -3,11 +3,11 @@ from IOUtils import IOUtils
 
 def saveProportionalReportingRatios(prrBySymptomByDrug, directory):
     shutil.rmtree(directory, ignore_errors = True)
-    drugByFilename = {}
+    filenameByDrug = {}
     i = 0
     for drug, prrBySymptom in prrBySymptomByDrug.items():
         i += 1
         filename = f'{i}.json'
-        drugByFilename[filename] = drug
+        filenameByDrug[drug] = filename
         IOUtils.saveDictAsJson(prrBySymptom, f'{directory}/{filename}')
-    IOUtils.saveDictAsJson(drugByFilename, f'{directory}/drugByFilename.json')    
+    IOUtils.saveDictAsJson(filenameByDrug, f'{directory}/filenameByDrug.json')    
diff --git a/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersisterTest.py b/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersisterTest.py
index 18fc00dd39d..5f412d384f3 100644
--- a/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersisterTest.py
+++ b/src/SymptomsCausedByVaccines/ProportionalReportingRatiosPersisterTest.py
@@ -26,8 +26,8 @@ class ProportionalReportingRatiosPersisterTest(unittest.TestCase):
             ProportionalReportingRatiosPersisterTest.readJsonFile(f'{directory}/{drugFilename}'),
             prrBySymptom)
         self.assertDictEqual(
-            ProportionalReportingRatiosPersisterTest.readJsonFile(f'{directory}/drugByFilename.json'),
-            { drugFilename: drug })
+            ProportionalReportingRatiosPersisterTest.readJsonFile(f'{directory}/filenameByDrug.json'),
+            { drug: drugFilename })
 
     @staticmethod
     def readJsonFile(file):