Move push_int_non_minimal to BuilderExtPriv

diff --git a/bitcoin/src/blockdata/constants.rs b/bitcoin/src/blockdata/constants.rs
index e7458f8b..2f1053e5 100644
--- a/bitcoin/src/blockdata/constants.rs
+++ b/bitcoin/src/blockdata/constants.rs
@@ -12,9 +12,10 @@ use crate::locktime::absolute;
 use crate::network::{Network, Params};
 use crate::opcodes::all::*;
 use crate::pow::CompactTarget;
+use crate::script::{self, BuilderExtPriv as _};
 use crate::transaction::{self, OutPoint, Transaction, TxIn, TxOut};
 use crate::witness::Witness;
-use crate::{script, Amount, BlockHash, BlockTime, Sequence, TestnetVersion};
+use crate::{Amount, BlockHash, BlockTime, Sequence, TestnetVersion};
 
 /// How many seconds between blocks we expect on average.
 pub const TARGET_BLOCK_SPACING: u32 = 600;
diff --git a/bitcoin/src/blockdata/script/builder.rs b/bitcoin/src/blockdata/script/builder.rs
index ace9d278..7a9f37f1 100644
--- a/bitcoin/src/blockdata/script/builder.rs
+++ b/bitcoin/src/blockdata/script/builder.rs
@@ -70,15 +70,6 @@ impl<T> Builder<T> {
         Self::from(script.into_bytes())
     }
 
-    /// Adds instructions to push an integer onto the stack without optimization.
-    ///
-    /// This uses the explicit encoding regardless of the availability of dedicated opcodes.
-    pub(in crate::blockdata) fn push_int_non_minimal(self, data: i64) -> Self {
-        let mut script = self.into_script();
-        script.push_int_non_minimal(data);
-        Self::from(script.into_bytes())
-    }
-
     /// Adds instructions to push some arbitrary data onto the stack.
     ///
     /// If the data can be exactly produced by a numeric opcode, that opcode
@@ -190,6 +181,25 @@ impl<T> Builder<T> {
     pub fn as_bytes(&self) -> &[u8] { self.as_script().as_bytes() }
 }
 
+mod sealed {
+    pub trait Sealed {}
+    impl<T> Sealed for super::Builder<T> {}
+}
+
+crate::internal_macros::define_extension_trait! {
+    /// Extension functionality for [`Builder`] that should be private.
+    pub(in crate::blockdata) trait BuilderExtPriv<T> impl<T> for Builder<T> {
+        /// Adds instructions to push an integer onto the stack without optimization.
+        ///
+        /// This uses the explicit encoding regardless of the availability of dedicated opcodes.
+        fn push_int_non_minimal(self, data: i64) -> Self {
+            let mut script = self.into_script();
+            script.push_int_non_minimal(data);
+            Self::from(script.into_bytes())
+        }
+    }
+}
+
 impl<T> Default for Builder<T> {
     fn default() -> Self { Self::new() }
 }
diff --git a/bitcoin/src/blockdata/script/mod.rs b/bitcoin/src/blockdata/script/mod.rs
index 10bc098a..b04488d4 100644
--- a/bitcoin/src/blockdata/script/mod.rs
+++ b/bitcoin/src/blockdata/script/mod.rs
@@ -85,6 +85,7 @@ pub use primitives::script::{
 };
 
 pub(crate) use self::borrowed::ScriptExtPriv;
+pub(in crate::blockdata) use self::builder::BuilderExtPriv;
 #[doc(no_inline)]
 pub use self::error::{
     Error, PushBytesError, RedeemScriptSizeError, ScriptIntError, WitnessScriptSizeError,