diff --git a/src/misc/bitvect.hh b/src/misc/bitvect.hh
index b641326d9..c1a44c89a 100644
--- a/src/misc/bitvect.hh
+++ b/src/misc/bitvect.hh
@@ -298,6 +298,23 @@ namespace spot
       return *this;
     }
 
+    bool is_subset_of(const bitvect& other) const
+    {
+      assert(other.block_count_ >= block_count_);
+
+      size_t i;
+      for (i = 0; i < block_count_ - 1; ++i)
+	if ((storage_[i] & other.storage_[i]) != other.storage_[i])
+	  return false;
+
+      // The last block might not be fully used, compare only the
+      // relevant portion.
+      const size_t bpb = 8 * sizeof(bitvect::block_t);
+      block_t mask = (1UL << (size() % bpb)) - 1;
+      return ((storage_[i] & mask & other.storage_[i])
+	      == (other.storage_[i] & mask));
+    }
+
     bool operator==(const bitvect& other) const
     {
       if (other.size_ != size_)
diff --git a/src/tgbatest/bitvect.cc b/src/tgbatest/bitvect.cc
index 4cd758a27..09b6ae608 100644
--- a/src/tgbatest/bitvect.cc
+++ b/src/tgbatest/bitvect.cc
@@ -64,6 +64,9 @@ int main()
   *x |= *w;
   ECHO(x);
 
+  std::cout << "subset? " << w->is_subset_of(*x)
+	    << ' ' << w->is_subset_of(*v) << '\n';
+
   for (size_t i = 0; i < 30; ++i)
     w->push_back((i & 3) == 0);
   ECHO(w);
diff --git a/src/tgbatest/bitvect.test b/src/tgbatest/bitvect.test
index 5407f5929..09534ca95 100755
--- a/src/tgbatest/bitvect.test
+++ b/src/tgbatest/bitvect.test
@@ -42,6 +42,7 @@ w: 000000000010110000000000000000100000000001
 
 x: 000000000000000000000000000000000000000000000000000000000000100000000010000
 x: 000000000010110000000000000000100000000001000000000000000000100000000010000
+subset? 1 0
 w: 000000000010110000000000000000100000000001100010001000100010001000100010
 x: 000000000010110000000000000000100000000001000000000000000000000000000010000
 x: 111111111111111111111111111111111111111111111111111111111111111111111111111