diff --git a/src/libslic3r/TriangleMesh.cpp b/src/libslic3r/TriangleMesh.cpp
index efd8e97f7..b33dd38cc 100644
--- a/src/libslic3r/TriangleMesh.cpp
+++ b/src/libslic3r/TriangleMesh.cpp
@@ -1190,11 +1190,11 @@ std::vector<indexed_triangle_set> its_split(const indexed_triangle_set &its)
 }
 
 // Number of disconnected patches (faces are connected if they share an edge, shared edge defined with 2 shared vertex indices).
-bool its_number_of_patches(const indexed_triangle_set &its)
+size_t its_number_of_patches(const indexed_triangle_set &its)
 {
     return its_number_of_patches<>(its);
 }
-bool its_number_of_patches(const indexed_triangle_set &its, const std::vector<Vec3i> &face_neighbors)
+size_t its_number_of_patches(const indexed_triangle_set &its, const std::vector<Vec3i> &face_neighbors)
 {
     return its_number_of_patches<>(ItsNeighborsWrapper{ its, face_neighbors });
 }
diff --git a/src/libslic3r/TriangleMesh.hpp b/src/libslic3r/TriangleMesh.hpp
index 951e351fe..459917ab9 100644
--- a/src/libslic3r/TriangleMesh.hpp
+++ b/src/libslic3r/TriangleMesh.hpp
@@ -219,8 +219,8 @@ std::vector<indexed_triangle_set> its_split(const indexed_triangle_set &its);
 std::vector<indexed_triangle_set> its_split(const indexed_triangle_set &its, std::vector<Vec3i> &face_neighbors);
 
 // Number of disconnected patches (faces are connected if they share an edge, shared edge defined with 2 shared vertex indices).
-bool its_number_of_patches(const indexed_triangle_set &its);
-bool its_number_of_patches(const indexed_triangle_set &its, const std::vector<Vec3i> &face_neighbors);
+size_t its_number_of_patches(const indexed_triangle_set &its);
+size_t its_number_of_patches(const indexed_triangle_set &its, const std::vector<Vec3i> &face_neighbors);
 // Same as its_number_of_patches(its) > 1, but faster.
 bool its_is_splittable(const indexed_triangle_set &its);
 bool its_is_splittable(const indexed_triangle_set &its, const std::vector<Vec3i> &face_neighbors);