diff --git a/storage/funcs.cpp b/storage/funcs.cpp
index d2ea8a51..5bbc5e80 100644
--- a/storage/funcs.cpp
+++ b/storage/funcs.cpp
@@ -16,17 +16,17 @@ void copy_3d_region_zxy(Span<uint8_t> dst, Vector3i dst_size, Vector3i dst_min,
 
 #ifdef DEBUG_ENABLED
 	if (src.data() == dst.data()) {
-		ERR_FAIL_COND_MSG(
-				Box3i::from_min_max(src_min, src_max).intersects(Box3i::from_min_max(dst_min, dst_min + area_size)),
+		ZN_ASSERT_RETURN_MSG(
+				!Box3i::from_min_max(src_min, src_max).intersects(Box3i::from_min_max(dst_min, dst_min + area_size)),
 				"Copy across the same buffer to an overlapping area is not supported");
 	}
-	ERR_FAIL_COND(Vector3iUtil::get_volume(area_size) * item_size > dst.size());
-	ERR_FAIL_COND(Vector3iUtil::get_volume(area_size) * item_size > src.size());
+	ZN_ASSERT_RETURN(Vector3iUtil::get_volume(area_size) * item_size <= dst.size());
+	ZN_ASSERT_RETURN(Vector3iUtil::get_volume(area_size) * item_size <= src.size());
 #endif
 
 	if (area_size == src_size && area_size == dst_size) {
 		// Copy everything
-		ERR_FAIL_COND(dst.size() != src.size());
+		ZN_ASSERT_RETURN(dst.size() == src.size());
 		memcpy(dst.data(), src.data(), dst.size());
 
 	} else {
@@ -42,8 +42,8 @@ void copy_3d_region_zxy(Span<uint8_t> dst, Vector3i dst_size, Vector3i dst_min,
 			unsigned int dst_ri = Vector3iUtil::get_zxy_index(Vector3i(dst_min + pos), dst_size) * item_size;
 			for (; pos.x < area_size.x; ++pos.x) {
 #ifdef DEBUG_ENABLED
-				ERR_FAIL_COND(dst_ri >= dst.size());
-				ERR_FAIL_COND(dst.size() - dst_ri < area_size.y * item_size);
+				ZN_ASSERT_RETURN(dst_ri < dst.size());
+				ZN_ASSERT_RETURN(dst.size() - dst_ri >= area_size.y * item_size);
 #endif
 				// TODO Cast src and dst to `restrict` so the optimizer can assume adresses don't overlap,
 				//      which might allow to write as a for loop (which may compile as a `memcpy`)?
diff --git a/storage/funcs.h b/storage/funcs.h
index 0b6fe78d..dd0471cc 100644
--- a/storage/funcs.h
+++ b/storage/funcs.h
@@ -68,7 +68,7 @@ void fill_3d_region_zxy(Span<T> dst, Vector3i dst_size, Vector3i dst_min, Vector
 	}
 
 #ifdef DEBUG_ENABLED
-	ERR_FAIL_COND(Vector3iUtil::get_volume(area_size) > dst.size());
+	ZN_ASSERT_RETURN(Vector3iUtil::get_volume(area_size) <= dst.size());
 #endif
 
 	if (area_size == dst_size) {
@@ -191,7 +191,7 @@ inline void debug_check_texture_indices(FixedArray<uint8_t, 4> indices) {
 	fill(checked, false);
 	for (unsigned int i = 0; i < indices.size(); ++i) {
 		unsigned int ti = indices[i];
-		CRASH_COND(checked[ti]);
+		ZN_ASSERT(!checked[ti]);
 		checked[ti] = true;
 	}
 }
@@ -211,7 +211,7 @@ struct IntBasis {
 			case Vector3i::AXIS_Z:
 				return z;
 			default:
-				CRASH_NOW();
+				ZN_CRASH();
 		}
 		return Vector3i();
 	}
@@ -222,11 +222,11 @@ struct IntBasis {
 // The array's coordinate convention uses ZXY (index+1 does Y+1).
 template <typename T>
 Vector3i transform_3d_array_zxy(Span<const T> src_grid, Span<T> dst_grid, Vector3i src_size, IntBasis basis) {
-	ERR_FAIL_COND_V(!Vector3iUtil::is_unit_vector(basis.x), src_size);
-	ERR_FAIL_COND_V(!Vector3iUtil::is_unit_vector(basis.y), src_size);
-	ERR_FAIL_COND_V(!Vector3iUtil::is_unit_vector(basis.z), src_size);
-	ERR_FAIL_COND_V(src_grid.size() != static_cast<size_t>(Vector3iUtil::get_volume(src_size)), src_size);
-	ERR_FAIL_COND_V(dst_grid.size() != static_cast<size_t>(Vector3iUtil::get_volume(src_size)), src_size);
+	ZN_ASSERT_RETURN_V(Vector3iUtil::is_unit_vector(basis.x), src_size);
+	ZN_ASSERT_RETURN_V(Vector3iUtil::is_unit_vector(basis.y), src_size);
+	ZN_ASSERT_RETURN_V(Vector3iUtil::is_unit_vector(basis.z), src_size);
+	ZN_ASSERT_RETURN_V(src_grid.size() == static_cast<size_t>(Vector3iUtil::get_volume(src_size)), src_size);
+	ZN_ASSERT_RETURN_V(dst_grid.size() == static_cast<size_t>(Vector3iUtil::get_volume(src_size)), src_size);
 
 	const int xa = basis.x.x != 0 ? 0 : basis.x.y != 0 ? 1 : 2;
 	const int ya = basis.y.x != 0 ? 0 : basis.y.y != 0 ? 1 : 2;