diff --git a/fake_home/.zshrc b/fake_home/.zshrc
index e8ad6a6..4191782 100644
--- a/fake_home/.zshrc
+++ b/fake_home/.zshrc
@@ -160,8 +160,13 @@ function sync-history {
     fi
     echo "Merging history files..."
     fc -W # Write to history file
-    merge-hist "$HOME/.histfile" "$HOME/.tmp/.histfile" > "$HOME/.tmp/$(whoami).histfile"
-    mv "$HOME/.tmp/$(whoami).histfile" "$HOME/.histfile"
+    local merged_name="$HOME/.tmp/$(whoami).histfile"
+    merge-hist "$HOME/.histfile" "$HOME/.tmp/.histfile" > "$merged_name"
+    if ! (($(cat "$merged_name" | wc -l) > $(cat "$HOME/.tmp/.histfile" | wc -l))); then
+        echo "Merged histfile '$merged_name' somehow smaller than current histfile"
+        return
+    fi
+    mv "$merged_name" "$HOME/.histfile"
     fc -R # Read from new history file
     echo "Uploading new shared history..."
     tscp -P 11275 "$HOME/.histfile" 'sage@sagev.space:~/histfile'