diff --git a/src/libslic3r/Format/OBJ.cpp b/src/libslic3r/Format/OBJ.cpp
index aa389781af..f0a002f50d 100644
--- a/src/libslic3r/Format/OBJ.cpp
+++ b/src/libslic3r/Format/OBJ.cpp
@@ -70,7 +70,8 @@ bool load_obj(const char *path, TriangleMesh *meshptr)
                 ++ num_normals;
             }
         }
-        if (data.vertices[i].coordIdx != -1) {
+        // Result of obj_parseline() call is not checked, thus not all vertices are necessarily finalized with coord_Idx == -1.
+        if (i < data.vertices.size() && data.vertices[i].coordIdx != -1) {
             // This is a quad. Produce the other triangle.
             stl_facet &facet2 = stl.facet_start[i_face++];
             facet2.vertex[0] = facet.vertex[0];
diff --git a/src/libslic3r/Format/objparser.cpp b/src/libslic3r/Format/objparser.cpp
index 8c1a53459d..f675bfd66e 100644
--- a/src/libslic3r/Format/objparser.cpp
+++ b/src/libslic3r/Format/objparser.cpp
@@ -338,11 +338,14 @@ bool objparse(const char *path, ObjData &data)
 					char *c = buf + lastLine;
 					while (*c == ' ' || *c == '\t')
 						++ c;
+					//FIXME check the return value and exit on error?
+					// Will it break parsing of some obj files?
 					obj_parseline(c, data);
 					lastLine = i + 1;
 				}
 			lenPrev = len - lastLine;
 			memmove(buf, buf + lastLine, lenPrev);
+			assert(lenPrev <= 65536);
 		}
     }
     catch (std::bad_alloc&) {