diff --git a/src/client/content_mapblock.cpp b/src/client/content_mapblock.cpp
index 297a07bcdca4..668ede08c95a 100644
--- a/src/client/content_mapblock.cpp
+++ b/src/client/content_mapblock.cpp
@@ -617,14 +617,14 @@ void MapblockMeshGenerator::calculateCornerLevels()
 		cur_liquid.corner_levels[k][i] = getCornerLevel(i, k);
 }
 
-f32 MapblockMeshGenerator::getCornerLevel(int i, int k)
+f32 MapblockMeshGenerator::getCornerLevel(int i, int k) const
 {
 	float sum = 0;
 	int count = 0;
 	int air_count = 0;
 	for (int dk = 0; dk < 2; dk++)
 	for (int di = 0; di < 2; di++) {
-		LiquidData::NeighborData &neighbor_data = cur_liquid.neighbors[k + dk][i + di];
+		const LiquidData::NeighborData &neighbor_data = cur_liquid.neighbors[k + dk][i + di];
 		content_t content = neighbor_data.content;
 
 		// If top is liquid, draw starting from top of node
diff --git a/src/client/content_mapblock.h b/src/client/content_mapblock.h
index 99abb7f99c71..730330a0344b 100644
--- a/src/client/content_mapblock.h
+++ b/src/client/content_mapblock.h
@@ -138,7 +138,7 @@ class MapblockMeshGenerator
 	void prepareLiquidNodeDrawing();
 	void getLiquidNeighborhood();
 	void calculateCornerLevels();
-	f32 getCornerLevel(int i, int k);
+	f32 getCornerLevel(int i, int k) const;
 	void drawLiquidSides();
 	void drawLiquidTop();
 	void drawLiquidBottom();