diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index f9d79ceeeb..43b966163f 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -178,6 +178,11 @@ update-preinstall() {
   then
     export HOMEBREW_AUTO_UPDATING="1"
 
+    if [[ -z "$HOMEBREW_AUTO_UPDATE_SECS" ]]
+    then
+      HOMEBREW_AUTO_UPDATE_SECS="300"
+    fi
+
     # Skip auto-update if the cask/core tap has been updated in the
     # last $HOMEBREW_AUTO_UPDATE_SECS.
     if [[ "$HOMEBREW_COMMAND" = "cask" ]]
diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index 388aefe003..bde417c994 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -342,11 +342,6 @@ EOS
     fi
   fi
 
-  if [[ -z "$HOMEBREW_AUTO_UPDATE_SECS" ]]
-  then
-    HOMEBREW_AUTO_UPDATE_SECS="300"
-  fi
-
   # check permissions
   if [[ -e "$HOMEBREW_CELLAR" && ! -w "$HOMEBREW_CELLAR" ]]
   then