diff --git a/findloop.c b/findloop.c
index e6b2654..30c128c 100644
--- a/findloop.c
+++ b/findloop.c
@@ -37,7 +37,7 @@ void findloop_free_state(struct findloopstate *state)
     sfree(state);
 }
 
-int findloop_is_loop_edge(struct findloopstate *pv, int u, int v)
+bool findloop_is_loop_edge(struct findloopstate *pv, int u, int v)
 {
     /*
      * Since the algorithm is intended for finding bridges, and a
@@ -56,8 +56,8 @@ int findloop_is_loop_edge(struct findloopstate *pv, int u, int v)
     return !(pv[u].bridge == v || pv[v].bridge == u);
 }
 
-int findloop_run(struct findloopstate *pv, int nvertices,
-                 neighbour_fn_t neighbour, void *ctx)
+bool findloop_run(struct findloopstate *pv, int nvertices,
+                  neighbour_fn_t neighbour, void *ctx)
 {
     int u, v, w, root, index;
     int nbridges, nedges;
diff --git a/puzzles.h b/puzzles.h
index d6d9e51..887af7b 100644
--- a/puzzles.h
+++ b/puzzles.h
@@ -580,22 +580,22 @@ void findloop_free_state(struct findloopstate *);
 typedef int (*neighbour_fn_t)(int vertex, void *ctx);
 /*
  * Actual function to find loops. 'ctx' will be passed unchanged to
- * the 'neighbour' function to query graph edges. Returns FALSE if no
- * loop was found, or TRUE if one was.
+ * the 'neighbour' function to query graph edges. Returns false if no
+ * loop was found, or true if one was.
  */
-int findloop_run(struct findloopstate *state, int nvertices,
-                 neighbour_fn_t neighbour, void *ctx);
+bool findloop_run(struct findloopstate *state, int nvertices,
+                  neighbour_fn_t neighbour, void *ctx);
 /*
  * Query whether an edge is part of a loop, in the output of
  * find_loops.
  *
  * Due to the internal storage format, if you pass u,v which are not
- * connected at all, the output will be TRUE. (The algorithm actually
+ * connected at all, the output will be true. (The algorithm actually
  * stores an exhaustive list of *non*-loop edges, because there are
  * fewer of those, so really it's querying whether the edge is on that
  * list.)
  */
-int findloop_is_loop_edge(struct findloopstate *state, int u, int v);
+bool findloop_is_loop_edge(struct findloopstate *state, int u, int v);
 
 /*
  * Data structure containing the function calls and data specific