diff --git a/marker/cleaners/headings.py b/marker/cleaners/headings.py
index 8cdcb9f6..8be2bfa8 100644
--- a/marker/cleaners/headings.py
+++ b/marker/cleaners/headings.py
@@ -63,6 +63,9 @@ def split_heading_blocks(pages: List[Page]):
 
 
 def bucket_headings(line_heights, num_levels=settings.HEADING_LEVEL_COUNT):
+    if len(line_heights) <= num_levels:
+        return []
+
     data = np.asarray(line_heights).reshape(-1, 1)
     labels = KMeans(n_clusters=num_levels, random_state=0, n_init="auto").fit_predict(data)
     data_labels = np.concatenate([data, labels.reshape(-1, 1)], axis=1)
@@ -119,5 +122,5 @@ def infer_heading_levels(pages: List[Page], height_tol=.99):
                     break
 
             if block.heading_level is None:
-                block.heading_level = min(len(heading_ranges), settings.HEADING_DEFAULT_LEVEL)
+                block.heading_level = settings.HEADING_DEFAULT_LEVEL
 
diff --git a/marker/postprocessors/markdown.py b/marker/postprocessors/markdown.py
index 5029df3a..fdf40a22 100644
--- a/marker/postprocessors/markdown.py
+++ b/marker/postprocessors/markdown.py
@@ -143,7 +143,7 @@ def block_separator(prev_block: FullyMergedBlock, block: FullyMergedBlock):
     return sep + block.text
 
 
-def merge_lines(blocks: List[List[MergedBlock]]):
+def merge_lines(blocks: List[List[MergedBlock]], max_block_gap=10):
     text_blocks = []
     prev_type = None
     prev_line = None
@@ -171,8 +171,9 @@ def merge_lines(blocks: List[List[MergedBlock]]):
                 line_height = line.bbox[3] - line.bbox[1]
                 prev_line_height = prev_line.bbox[3] - prev_line.bbox[1] if prev_line else 0
                 prev_line_x = prev_line.bbox[0] if prev_line else 0
+                vertical_dist = min(abs(line.bbox[1] - prev_line.bbox[3]), abs(line.bbox[3] - prev_line.bbox[1])) if prev_line else 0
                 prev_line = line
-                is_continuation = line_height == prev_line_height and line.bbox[0] == prev_line_x
+                is_continuation = line_height == prev_line_height and line.bbox[0] == prev_line_x and vertical_dist < max_block_gap
                 if block_text:
                     block_text = line_separator(block_text, line.text, block_type, is_continuation)
                 else: