diff --git a/src/SIL.Machine/PunctuationAnalysis/ParatextProjectQuoteConventionDetector.cs b/src/SIL.Machine/PunctuationAnalysis/ParatextProjectQuoteConventionDetector.cs
index 93fbe81c..1812fad4 100644
--- a/src/SIL.Machine/PunctuationAnalysis/ParatextProjectQuoteConventionDetector.cs
+++ b/src/SIL.Machine/PunctuationAnalysis/ParatextProjectQuoteConventionDetector.cs
@@ -35,7 +35,7 @@ public QuoteConventionAnalysis GetQuoteConventionAnalysis(
         {
             return GetQuoteConventionAnalysis(
                 handler,
-                includeChapters.ToDictionary(kvp => Canon.BookIdToNumber(kvp.Key), kvp => kvp.Value)
+                includeChapters?.ToDictionary(kvp => Canon.BookIdToNumber(kvp.Key), kvp => kvp.Value)
             );
         }