diff --git a/Gemfile.lock b/Gemfile.lock
index cf00d96eea..fac393d0f2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -36,7 +36,7 @@ GEM
     cucumber-messages (22.0.0)
     cucumber-tag-expressions (6.1.1)
     diff-lcs (1.5.1)
-    ffi (1.17.0-arm64-darwin)
+    ffi (1.17.0)
     mini_mime (1.1.5)
     multi_test (1.1.0)
     rspec-expectations (3.13.3)
diff --git a/prelude.scm b/prelude.scm
index 92894c03ee..af05735f67 100644
--- a/prelude.scm
+++ b/prelude.scm
@@ -1576,7 +1576,7 @@
   (import (stak base))
 
   (begin
-    (define $halt (primitive 19))
+    (define $halt (primitive 18))
     (define $read-input (primitive 100))
     (define $write-output (primitive 101))
     (define $write-error (primitive 102))
@@ -2377,7 +2377,7 @@
     (only (stak base) data-rib code-points->string primitive procedure-type))
 
   (begin
-    (define $halt (primitive 19))
+    (define $halt (primitive 18))
     (define $command-line (primitive 300))
     (define $get-environment-variables (primitive 301))
 
diff --git a/r7rs/src/small.rs b/r7rs/src/small.rs
index e27ab6ddf9..aa7087077e 100644
--- a/r7rs/src/small.rs
+++ b/r7rs/src/small.rs
@@ -115,19 +115,6 @@ impl<D: Device, F: FileSystem, P: ProcessContext, C: Clock> SmallPrimitiveSet<D,
                 .into()
         })
     }
-
-    fn check_type(memory: &mut Memory, r#type: Type) -> Result<(), Error> {
-        Self::operate_top(memory, |memory, value| {
-            memory
-                .boolean(
-                    value
-                        .to_cons()
-                        .map(|cons| memory.cdr(cons).tag() == r#type as _)
-                        .unwrap_or_default(),
-                )
-                .into()
-        })
-    }
 }
 
 impl<D: Device, F: FileSystem, P: ProcessContext, C: Clock> PrimitiveSet