diff --git a/core/dive.cpp b/core/dive.cpp
index 82f32cdf4..9f60701b0 100644
--- a/core/dive.cpp
+++ b/core/dive.cpp
@@ -2265,7 +2265,7 @@ merge_result merge_dives(const struct dive &a_in, const struct dive &b_in, int o
 	}
 
 	const dive *a = &a_in;
-	const dive *b = &a_in;
+	const dive *b = &b_in;
 	if (is_dc_planner(&a->dcs[0]))
 		std::swap(a, b);