diff --git a/toolkit/components/places/src/nsNavHistory.cpp b/toolkit/components/places/src/nsNavHistory.cpp
index 1cf38c45be0f..d02a195c77e6 100644
--- a/toolkit/components/places/src/nsNavHistory.cpp
+++ b/toolkit/components/places/src/nsNavHistory.cpp
@@ -303,6 +303,7 @@ nsNavHistory::nsNavHistory() : mNowValid(PR_FALSE),
                                mExpireDaysMin(0),
                                mExpireDaysMax(0),
                                mExpireSites(0),
+                               mNumVisitsForFrecency(10),
                                mAutoCompleteOnlyTyped(PR_FALSE),
                                mAutoCompleteMaxResults(25),
                                mAutoCompleteSearchChunkSize(100),