diff --git a/build/parser.rs b/build/parser.rs
index 090e0b6a2a..2dc2464053 100644
--- a/build/parser.rs
+++ b/build/parser.rs
@@ -514,7 +514,11 @@ impl MavMessage {
                 // If sent by an implementation that doesn't have the extensions fields
                 // then the recipient will see zero values for the extensions fields.
                 let serde_default = if field.is_extension {
-                    quote!(#[cfg_attr(feature = "serde", serde(default))])
+                    if field.enumtype.is_some() {
+                        quote!(#[cfg_attr(feature = "serde", serde(default))])
+                    } else {
+                        quote!(#[cfg_attr(feature = "serde", serde(default = "crate::RustDefault::rust_default"))])
+                    }
                 } else {
                     quote!()
                 };
diff --git a/src/lib.rs b/src/lib.rs
index 3ab42ac8af..5186bd8e76 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -37,7 +37,7 @@ pub use self::connection::{connect, MavConnection};
 
 mod utils;
 #[allow(unused_imports)]
-use utils::remove_trailing_zeroes;
+use utils::{remove_trailing_zeroes, RustDefault};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
diff --git a/src/utils.rs b/src/utils.rs
index 1b814023bc..8cbd522c7f 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -17,3 +17,95 @@ pub(crate) fn remove_trailing_zeroes(data: &mut [u8]) -> usize {
 
     len
 }
+
+/// A trait very similar to `Default` but is only implemented for the equivalent Rust types to
+/// `MavType`s. This is only needed because rust doesn't currently implement `Default` for arrays
+/// of all sizes. In particular this trait is only ever used when the "serde" feature is enabled.
+pub(crate) trait RustDefault: Copy {
+    fn rust_default() -> Self;
+}
+
+impl<T: RustDefault, const N: usize> RustDefault for [T; N] {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        let val: T = RustDefault::rust_default();
+        [val; N]
+    }
+}
+
+impl RustDefault for u8 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for i8 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for u16 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for i16 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for u32 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for i32 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for u64 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for i64 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0
+    }
+}
+
+impl RustDefault for char {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        '\0'
+    }
+}
+
+impl RustDefault for f32 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0.0
+    }
+}
+
+impl RustDefault for f64 {
+    #[inline(always)]
+    fn rust_default() -> Self {
+        0.0
+    }
+}