diff --git a/hdbscan/hdbscan_.py b/hdbscan/hdbscan_.py
index 6ce07964..181df732 100644
--- a/hdbscan/hdbscan_.py
+++ b/hdbscan/hdbscan_.py
@@ -1299,6 +1299,12 @@ def generate_branch_detection_data(self):
         branches within clusters. This data is only useful if you are 
         intending to use functions from ``hdbscan.branches``.
         """
+        if self._min_spanning_tree is None:
+            raise ValueError("Branch prediction requires a minimum spanning tree; please re-run "
+                             "with `branch_repdiction_data=True` or at least `gen_min_spanning_tree=True` "
+                             "and this this function to generate the required information for branch "
+                             "branch detection."
+            )
         if self.metric in FAST_METRICS:
             min_samples = self.min_samples or self.min_cluster_size
             if self.metric in KDTREE_VALID_METRICS:
diff --git a/hdbscan/tests/test_branches.py b/hdbscan/tests/test_branches.py
index 5a6d9a36..c9bd281c 100644
--- a/hdbscan/tests/test_branches.py
+++ b/hdbscan/tests/test_branches.py
@@ -184,9 +184,7 @@ def test_branch_detection_data_with_unsupported_input():
 def test_generate_branch_detection_data():
     """Generate branch detection data function does not re-generate MST."""
     c = HDBSCAN(min_cluster_size=5).fit(X)
-    c.generate_branch_detection_data()
-    assert c.branch_detection_data_ is not None
-    assert_raises(AttributeError, lambda: c.minimum_spanning_tree_)
+    assert_raises(ValueError, c.generate_branch_detection_data)
 
 
 # --- Detecting Branches
@@ -287,15 +285,12 @@ def test_badargs():
     c = HDBSCAN(min_cluster_size=5, branch_detection_data=True).fit(X)
     c_nofit = HDBSCAN(min_cluster_size=5, branch_detection_data=True)
     c_nobranch = HDBSCAN(min_cluster_size=5, gen_min_span_tree=True).fit(X)
-    c_nomst = HDBSCAN(min_cluster_size=5).fit(X)
-    c_nomst.generate_branch_detection_data()
 
     assert_raises(AttributeError, detect_branches_in_clusters, "fail")
     assert_raises(AttributeError, detect_branches_in_clusters, None)
     assert_raises(AttributeError, detect_branches_in_clusters, "fail")
     assert_raises(ValueError, detect_branches_in_clusters, c_nofit)
     assert_raises(AttributeError, detect_branches_in_clusters, c_nobranch)
-    assert_raises(ValueError, detect_branches_in_clusters, c_nomst)
     assert_raises(ValueError, detect_branches_in_clusters, c, min_branch_size=-1)
     assert_raises(ValueError, detect_branches_in_clusters, c, min_branch_size=0)
     assert_raises(ValueError, detect_branches_in_clusters, c, min_branch_size=1)