diff --git a/machine/scripture/parse.py b/machine/scripture/parse.py
index a0ff8dc..73611a9 100644
--- a/machine/scripture/parse.py
+++ b/machine/scripture/parse.py
@@ -1,9 +1,14 @@
+import re
 from typing import Dict, List, Set, Union
 
 from .canon import book_id_to_number
 from .constants import ORIGINAL_VERSIFICATION
 from .verse_ref import Versification
 
+COMMA_SEPARATED_BOOKS = re.compile(r"([A-Z\d]{3}|OT|NT)(, ?([A-Z\d]{3}|OT|NT))*")
+BOOK_RANGE = re.compile(r"[A-Z\d]{3}-[A-Z\d]{3}")
+CHAPTER_SELECTION = re.compile(r"[A-Z\d]{3} ?(\d+|\d+-\d+)(, ?(\d+|\d+-\d+))*")
+
 
 def get_books(books: Union[str, List[str]]) -> Set[int]:
     if isinstance(books, str):
@@ -43,13 +48,29 @@ def get_chapters(
     chapters = {}
 
     if isinstance(chapter_selections, str):
-        if ";" not in chapter_selections and not any(
-            s.isdigit() and (i == len(chapter_selections) - 1 or not chapter_selections[i + 1].isalpha())
-            for i, s in enumerate(chapter_selections)
-        ):  # Backwards compatibility with get_books syntax:
+        chapter_selections = chapter_selections.strip()
+
+        if ";" in chapter_selections:
+            chapter_selections = chapter_selections.split(";")
+        elif re.fullmatch(COMMA_SEPARATED_BOOKS, chapter_selections) is not None:
             chapter_selections = chapter_selections.split(",")
+        elif chapter_selections.startswith("-"):
+            raise ValueError(f"Cannot subtract before adding sections: {chapter_selections}")
+        elif re.search(BOOK_RANGE, chapter_selections):
+            if len(chapter_selections) == 7:
+                chapter_selections = [chapter_selections]
+            else:
+                raise ValueError(
+                    "Invalid syntax. If one of your selections is a range of books, \
+                    selections must be seprated with semicolons."
+                )
+        elif re.fullmatch(CHAPTER_SELECTION, chapter_selections) is None:
+            raise ValueError(
+                "Invalid syntax. If one of your selections includes specific chapters or subtraction, \
+                selections must be separated with semicolons."
+            )
         else:
-            chapter_selections = chapter_selections.split(";")
+            chapter_selections = [chapter_selections]
 
     for section in chapter_selections:
         section = section.strip()
diff --git a/tests/scripture/test_parse.py b/tests/scripture/test_parse.py
index fa9e800..be11f63 100644
--- a/tests/scripture/test_parse.py
+++ b/tests/scripture/test_parse.py
@@ -43,10 +43,6 @@ def test_get_chapters() -> None:
     whole_bible = {i: [] for i in range(1, 67)}
     assert get_chapters("NT,OT") == whole_bible
 
-    del whole_bible[2]  # EXO
-    del whole_bible[41]  # MRK
-    assert get_chapters("NT,OT,-MRK,-EXO") == whole_bible
-
     assert get_chapters("MAT;MRK") == {40: [], 41: []}
     assert get_chapters("MAT; MRK") == {40: [], 41: []}
     assert get_chapters("MAT1,2,3") == {40: [1, 2, 3]}
@@ -57,7 +53,10 @@ def test_get_chapters() -> None:
     assert get_chapters("2JN-3JN;EXO1,8,3-5;GEN") == {1: [], 2: [1, 3, 4, 5, 8], 63: [], 64: []}
     assert get_chapters("1JN 1;1JN 2;1JN 3-5") == {62: []}
     assert get_chapters("MAT-ROM;-ACT4-28") == {40: [], 41: [], 42: [], 43: [], 44: [1, 2, 3], 45: []}
+    assert get_chapters("2JN;-2JN 1") == {}
 
+    del whole_bible[2]  # EXO
+    del whole_bible[41]  # MRK
     assert get_chapters("NT;OT;-MRK;-EXO") == whole_bible
     test_bible = {i: [] for i in range(40, 67)}
     test_chapters_mat = [1, 2] + [i for i in range(6, 17)] + [i for i in range(18, 29)]
@@ -110,3 +109,11 @@ def test_get_chapters() -> None:
         get_chapters("NT;OT;-ABC")
     with raises(ValueError):
         get_chapters("MAT;-ABC 1")
+
+    # mixing old (comma-separated) and new syntax
+    with raises(ValueError):
+        get_chapters("NT,OT,-MRK,-EXO")
+    with raises(ValueError):
+        get_chapters("OT,MAT1")
+    with raises(ValueError):
+        get_chapters("OT,MAT-LUK")