diff --git a/stm32-data-gen/src/chips.rs b/stm32-data-gen/src/chips.rs
index a62cb68..ff585d2 100644
--- a/stm32-data-gen/src/chips.rs
+++ b/stm32-data-gen/src/chips.rs
@@ -692,8 +692,8 @@ fn process_core(
     };
     let chip_nvic = group.ips.values().find(|x| x.name == want_nvic_name).unwrap();
 
-    // With the current data sources, this value is always either 2 or 4, and never unwraps to None(0)
-    let nvic_priority_bits = *(defines.0.get("__NVIC_PRIO_BITS").unwrap_or(&0)) as u8;
+    // With the current data sources, this value is always either 2 or 4, and never resolves to None
+    let nvic_priority_bits = defines.0.get("__NVIC_PRIO_BITS").map(|bits| *bits as u8);
 
     let mut header_irqs = h.interrupts.get(core_name).unwrap().clone();
     let chip_irqs = chip_interrupts
diff --git a/stm32-data-serde/src/lib.rs b/stm32-data-serde/src/lib.rs
index 46fc255..dd44b07 100644
--- a/stm32-data-serde/src/lib.rs
+++ b/stm32-data-serde/src/lib.rs
@@ -62,7 +62,8 @@ pub mod chip {
     pub struct Core {
         pub name: String,
         pub peripherals: Vec<core::Peripheral>,
-        pub nvic_priority_bits: u8,
+        #[serde(skip_serializing_if = "Option::is_none")]
+        pub nvic_priority_bits: Option<u8>,
         pub interrupts: Vec<core::Interrupt>,
         pub dma_channels: Vec<core::DmaChannels>,
     }
diff --git a/stm32-metapac-gen/res/src/metadata.rs b/stm32-metapac-gen/res/src/metadata.rs
index 3e7efc0..2342765 100644
--- a/stm32-metapac-gen/res/src/metadata.rs
+++ b/stm32-metapac-gen/res/src/metadata.rs
@@ -5,7 +5,7 @@ pub struct Metadata {
     pub line: &'static str,
     pub memory: &'static [MemoryRegion],
     pub peripherals: &'static [Peripheral],
-    pub nvic_priority_bits: u8,
+    pub nvic_priority_bits: Option<u8>,
     pub interrupts: &'static [Interrupt],
     pub dma_channels: &'static [DmaChannel],
 }
diff --git a/stm32-metapac-gen/src/data.rs b/stm32-metapac-gen/src/data.rs
index 3298398..38e85d6 100644
--- a/stm32-metapac-gen/src/data.rs
+++ b/stm32-metapac-gen/src/data.rs
@@ -38,7 +38,8 @@ pub enum MemoryRegionKind {
 pub struct Core {
     pub name: String,
     pub peripherals: Vec<Peripheral>,
-    pub nvic_priority_bits: u8,
+    #[serde(default)]
+    pub nvic_priority_bits: Option<u8>,
     pub interrupts: Vec<Interrupt>,
     pub dma_channels: Vec<DmaChannel>,
 }
diff --git a/stm32-metapac-gen/src/lib.rs b/stm32-metapac-gen/src/lib.rs
index 4a91e2c..f2599b9 100644
--- a/stm32-metapac-gen/src/lib.rs
+++ b/stm32-metapac-gen/src/lib.rs
@@ -195,7 +195,7 @@ impl Gen {
                 line: {:?},
                 memory: {},
                 peripherals: PERIPHERALS,
-                nvic_priority_bits: {},
+                nvic_priority_bits: {:?},
                 interrupts: INTERRUPTS,
                 dma_channels: DMA_CHANNELS,
             }};",