diff --git a/appendix-D/01_main-chapter-code/previous_chapters.py b/appendix-D/01_main-chapter-code/previous_chapters.py
index 275eac9..4292f64 100644
--- a/appendix-D/01_main-chapter-code/previous_chapters.py
+++ b/appendix-D/01_main-chapter-code/previous_chapters.py
@@ -255,7 +255,9 @@ def calc_loss_batch(input_batch, target_batch, model, device):
 
 def calc_loss_loader(data_loader, model, device, num_batches=None):
     total_loss = 0.
-    if num_batches is None:
+    if len(data_loader) == 0:
+        return float("nan")
+    elif num_batches is None:
         num_batches = len(data_loader)
     else:
         num_batches = min(num_batches, len(data_loader))
diff --git a/ch05/01_main-chapter-code/ch05.ipynb b/ch05/01_main-chapter-code/ch05.ipynb
index afe1300..4b01496 100644
--- a/ch05/01_main-chapter-code/ch05.ipynb
+++ b/ch05/01_main-chapter-code/ch05.ipynb
@@ -1090,7 +1090,9 @@
     "\n",
     "def calc_loss_loader(data_loader, model, device, num_batches=None):\n",
     "    total_loss = 0.\n",
-    "    if num_batches is None:\n",
+    "    if len(data_loader) == 0:\n",
+    "        return float(\"nan\")\n",
+    "    elif num_batches is None:\n",
     "        num_batches = len(data_loader)\n",
     "    else:\n",
     "        # Reduce the number of batches to match the total number of batches in the data loader\n",
diff --git a/ch05/01_main-chapter-code/gpt_train.py b/ch05/01_main-chapter-code/gpt_train.py
index b333291..d025d76 100644
--- a/ch05/01_main-chapter-code/gpt_train.py
+++ b/ch05/01_main-chapter-code/gpt_train.py
@@ -34,7 +34,9 @@ def calc_loss_batch(input_batch, target_batch, model, device):
 
 def calc_loss_loader(data_loader, model, device, num_batches=None):
     total_loss = 0.
-    if num_batches is None:
+    if len(data_loader) == 0:
+        return float("nan")
+    elif num_batches is None:
         num_batches = len(data_loader)
     else:
         num_batches = min(num_batches, len(data_loader))
diff --git a/ch05/03_bonus_pretraining_on_gutenberg/previous_chapters.py b/ch05/03_bonus_pretraining_on_gutenberg/previous_chapters.py
index b79348d..a5ded8e 100644
--- a/ch05/03_bonus_pretraining_on_gutenberg/previous_chapters.py
+++ b/ch05/03_bonus_pretraining_on_gutenberg/previous_chapters.py
@@ -249,7 +249,9 @@ def calc_loss_batch(input_batch, target_batch, model, device):
 
 def calc_loss_loader(data_loader, model, device, num_batches=None):
     total_loss = 0.
-    if num_batches is None:
+    if len(data_loader) == 0:
+        return float("nan")
+    elif num_batches is None:
         num_batches = len(data_loader)
     else:
         num_batches = min(num_batches, len(data_loader))
diff --git a/ch05/05_bonus_hparam_tuning/hparam_search.py b/ch05/05_bonus_hparam_tuning/hparam_search.py
index c207357..94cfb0d 100644
--- a/ch05/05_bonus_hparam_tuning/hparam_search.py
+++ b/ch05/05_bonus_hparam_tuning/hparam_search.py
@@ -26,7 +26,9 @@ HPARAM_GRID = {
 
 def calc_loss_loader(data_loader, model, device, num_batches=None):
     total_loss = 0.
-    if num_batches is None:
+    if len(data_loader) == 0:
+        return float("nan")
+    elif num_batches is None:
         num_batches = len(data_loader)
     else:
         num_batches = min(num_batches, len(data_loader))