diff --git a/factorygame/data/models.py b/factorygame/data/models.py
index a294ae4..f561d5a 100644
--- a/factorygame/data/models.py
+++ b/factorygame/data/models.py
@@ -5,8 +5,8 @@ from typing import Optional
 from sqlalchemy import String, Select, select, Table, Column, ForeignKey
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
 
-amount_number = re.compile(r"^\d*(\.\d+)?")
-time_number = re.compile(r"^(\d+) seconds?")
+amount_per_step_regex = re.compile(r"^\d*(\.\d+)?")
+time_per_step_regex = re.compile(r"^(\d+(\.\d+)?) seconds?")
 
 
 class Base(DeclarativeBase):
@@ -83,11 +83,20 @@ class ResourceFlow(Base):
     time: Mapped[str]
 
     def amount_per_minute(self) -> float:
-        per_crafting_step_str = amount_number.match(self.amount).group(0)
-        per_crafting_step = float(per_crafting_step_str)
-        crafting_time_seconds_str = time_number.match(self.time).group(1)
-        crafting_time_seconds = float(crafting_time_seconds_str)
-        return per_crafting_step * (60.0 / crafting_time_seconds)
+        amount_per_step_match = amount_per_step_regex.match(self.amount)
+        assert amount_per_step_match, (
+            f"Amount per crafting step of resource {self.resource.label} in crafting recipe "
+            f"{self.result_of or self.ingredient_in} could not be parsed"
+        )
+        amount_per_step = float(amount_per_step_match.group(0))
+
+        time_per_step_match = time_per_step_regex.match(self.time)
+        assert time_per_step_match, (
+            f"Time per crafting step of resource {self.resource.label} in crafting recipe "
+            f"{self.result_of or self.ingredient_in} could not be parsed"
+        )
+        time_per_step = float(time_per_step_match.group(1))
+        return amount_per_step * (60.0 / time_per_step)
 
     def describe(self) -> str:
         return f"{repr(str(self.resource.label))}x{self.amount}"
@@ -120,4 +129,6 @@ class Recipe(Base):
         )
 
     def __repr__(self):
-        return f"Recipe(id={self.id}, factories={self.factories}, ingredients={self.ingredients}, results={self.results})"
+        return (
+            f"Recipe(id={self.id}, factories={self.factories}, ingredients={self.ingredients}, results={self.results})"
+        )