diff --git a/changelog_entry.yaml b/changelog_entry.yaml
index e69de29bb2d..f1f30d7d5bf 100644
--- a/changelog_entry.yaml
+++ b/changelog_entry.yaml
@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+      - Set household_weight default value to 1 to prevent microdf errors in Python 3.13.
diff --git a/policyengine_us/tests/policy/baseline/household/demographic/weights/household_weight.yaml b/policyengine_us/tests/policy/baseline/household/demographic/weights/household_weight.yaml
new file mode 100644
index 00000000000..31d12233af5
--- /dev/null
+++ b/policyengine_us/tests/policy/baseline/household/demographic/weights/household_weight.yaml
@@ -0,0 +1,6 @@
+- name: Household weight defaults to 1 when not specified
+  period: 2024
+  input:
+    employment_income: 50_000
+  output:
+    household_weight: 1
diff --git a/policyengine_us/variables/household/demographic/weights/household_weight.py b/policyengine_us/variables/household/demographic/weights/household_weight.py
index deaabf5c010..dced208b818 100644
--- a/policyengine_us/variables/household/demographic/weights/household_weight.py
+++ b/policyengine_us/variables/household/demographic/weights/household_weight.py
@@ -6,4 +6,5 @@ class household_weight(Variable):
     entity = Household
     label = "Household weight"
     definition_period = YEAR
+    default_value = 1
     uprating = "calibration.gov.census.populations.total"