diff --git a/.changes/unreleased/fixed-20260901-020000.yaml b/.changes/unreleased/fixed-20260901-020000.yaml
new file mode 100644
index 00000000..26299d3b
--- /dev/null
+++ b/.changes/unreleased/fixed-20260901-020000.yaml
@@ -0,0 +1,3 @@
+kind: Fixed
+body: Generated proto2 defaults for `inf`, `-inf`, and `nan` now use absolute primitive paths, so protobuf packages or modules named `f32` or `f64` cannot shadow them.
+time: 2026-09-01T02:00:00+02:00
diff --git a/buffa-codegen/src/defaults.rs b/buffa-codegen/src/defaults.rs
index 1f30545f..ace9aa5f 100644
--- a/buffa-codegen/src/defaults.rs
+++ b/buffa-codegen/src/defaults.rs
@@ -221,23 +221,23 @@ where
     match s {
         "inf" | "infinity" => {
             if is_f32 {
-                Ok(quote! { f32::INFINITY })
+                Ok(quote! { ::core::primitive::f32::INFINITY })
             } else {
-                Ok(quote! { f64::INFINITY })
+                Ok(quote! { ::core::primitive::f64::INFINITY })
             }
         }
         "-inf" | "-infinity" => {
             if is_f32 {
-                Ok(quote! { f32::NEG_INFINITY })
+                Ok(quote! { ::core::primitive::f32::NEG_INFINITY })
             } else {
-                Ok(quote! { f64::NEG_INFINITY })
+                Ok(quote! { ::core::primitive::f64::NEG_INFINITY })
             }
         }
         "nan" => {
             if is_f32 {
-                Ok(quote! { f32::NAN })
+                Ok(quote! { ::core::primitive::f32::NAN })
             } else {
-                Ok(quote! { f64::NAN })
+                Ok(quote! { ::core::primitive::f64::NAN })
             }
         }
         _ => {
@@ -514,19 +514,22 @@ mod tests {
     #[test]
     fn parse_float_inf() {
         let ts = parse_float_default::<f32>("inf").unwrap();
-        assert!(ts.to_string().contains("INFINITY"));
+        assert_eq!(ts.to_string(), ":: core :: primitive :: f32 :: INFINITY");
     }
 
     #[test]
     fn parse_float_neg_inf() {
         let ts = parse_float_default::<f64>("-inf").unwrap();
-        assert!(ts.to_string().contains("NEG_INFINITY"));
+        assert_eq!(
+            ts.to_string(),
+            ":: core :: primitive :: f64 :: NEG_INFINITY"
+        );
     }
 
     #[test]
     fn parse_float_nan() {
         let ts = parse_float_default::<f32>("nan").unwrap();
-        assert!(ts.to_string().contains("NAN"));
+        assert_eq!(ts.to_string(), ":: core :: primitive :: f32 :: NAN");
     }
 
     #[test]
diff --git a/buffa-test/build.rs b/buffa-test/build.rs
index e971ad2a..dd6beaaf 100644
--- a/buffa-test/build.rs
+++ b/buffa-test/build.rs
@@ -237,6 +237,17 @@ fn main() {
         .compile()
         .expect("buffa_build failed for prelude_shadow.proto");
 
+    // Special float defaults in a package named `f32` must not resolve
+    // against generated `f32`/`f64` modules. The nested extension constants
+    // deliberately occupy all six shadowable paths; compilation is the
+    // regression assertion.
+    buffa_build::Config::new()
+        .files(&["protos/float_default_shadow.proto"])
+        .includes(&["protos/"])
+        .generate_views(false)
+        .compile()
+        .expect("buffa_build failed for float_default_shadow.proto");
+
     // Nested-package pair (gh#80) — `test.nestpkg` + `test.nestpkg.inner`.
     // `lib.rs` wraps these with the same `pub mod a { use super::*; pub mod
     // a_b { use super::*; … } }` chain that `buffa-build`'s `_include.rs`
diff --git a/buffa-test/protos/float_default_shadow.proto b/buffa-test/protos/float_default_shadow.proto
new file mode 100644
index 00000000..d9fc4811
--- /dev/null
+++ b/buffa-test/protos/float_default_shadow.proto
@@ -0,0 +1,30 @@
+syntax = "proto2";
+
+package f32;
+
+message F32 {
+  extensions 100 to 200;
+  extend F32 {
+    optional float INFINITY = 100;
+    optional float NEG_INFINITY = 101;
+    optional float NAN = 102;
+  }
+}
+
+message F64 {
+  extensions 200 to 300;
+  extend F64 {
+    optional double INFINITY = 200;
+    optional double NEG_INFINITY = 201;
+    optional double NAN = 202;
+  }
+}
+
+message Defaults {
+  required float pos_inf = 1 [default = inf];
+  required float neg_inf = 2 [default = -inf];
+  required float nan_value = 3 [default = nan];
+  required double double_pos_inf = 4 [default = inf];
+  required double double_neg_inf = 5 [default = -inf];
+  required double double_nan = 6 [default = nan];
+}
diff --git a/buffa-test/src/lib.rs b/buffa-test/src/lib.rs
index 3e7b3199..5fc13fc4 100644
--- a/buffa-test/src/lib.rs
+++ b/buffa-test/src/lib.rs
@@ -553,6 +553,11 @@ pub mod prelude_shadow {
     buffa::include_proto!("test.prelude_shadow");
 }
 
+#[allow(clippy::derivable_impls, clippy::match_single_binding, dead_code)]
+pub mod float_default_shadow {
+    buffa::include_proto!("f32");
+}
+
 // Nested-package pair, wrapped exactly the way `buffa-build`'s
 // `_include.rs` would. The chain of `use super::*;` glob imports makes the
 // outer package's `__buffa` reachable from `inner`'s scope, which is the