diff --git a/sopel/modules/dice.py b/sopel/modules/dice.py
index 2f8c559eab..0e5336533c 100644
--- a/sopel/modules/dice.py
+++ b/sopel/modules/dice.py
@@ -124,10 +124,10 @@ def get_number_of_faces(self):
 def _roll_dice(bot, dice_expression):
     result = re.search(
         r"""
-        (?P<dice_num>\d*)
+        (?P<dice_num>-?\d*)
         d
-        (?P<dice_type>\d+)
-        (v(?P<drop_lowest>\d+))?
+        (?P<dice_type>-?\d+)
+        (v(?P<drop_lowest>-?\d+))?
         $""",
         dice_expression,
         re.IGNORECASE | re.VERBOSE)
@@ -140,6 +140,11 @@ def _roll_dice(bot, dice_expression):
         bot.reply("I don't have any dice with %d sides. =(" % dice_type)
         return None  # Signal there was a problem
 
+    # Can't roll a negative number of dice.
+    if dice_num < 0:
+        bot.reply("I'd rather not roll a negative amount of dice. =(")
+        return None # Signal there was a problem
+
     # Upper limit for dice should be at most a million. Creating a dict with
     # more than a million elements already takes a noticeable amount of time
     # on a fast computer and ~55kB of memory.
@@ -151,7 +156,10 @@ def _roll_dice(bot, dice_expression):
 
     if result.group('drop_lowest'):
         drop = int(result.group('drop_lowest'))
-        dice.drop_lowest(drop)
+        if drop >= 0:
+            dice.drop_lowest(drop)
+        else:
+            bot.reply("I can't drop the lowest %d dice. =(" % drop)
 
     return dice
 
@@ -176,7 +184,7 @@ def roll(bot, trigger):
     """
     # This regexp is only allowed to have one captured group, because having
     # more would alter the output of re.findall.
-    dice_regexp = r"\d*d\d+(?:v\d+)?"
+    dice_regexp = r"-?\d*[dD]-?\d+(?:[vV]-?\d+)?"
 
     # Get a list of all dice expressions, evaluate them and then replace the
     # expressions in the original string with the results. Replacing is done