diff --git a/src/include/Int64.h b/src/include/Int64.h
index 6033aa2..8e917dd 100644
--- a/src/include/Int64.h
+++ b/src/include/Int64.h
@@ -69,7 +69,7 @@
 
 #include <stddef.h>
 
-#if 0 /* TODO REMOVE */
+#ifndef INT64_FORCE_EMULATED
 
 #define BIT64_MAX 18446744073709551615UL
 
@@ -85,7 +85,7 @@ typedef signed long Int64;
 
 #endif
 
-#endif /* TODO REMOVE */
+#endif /* ifndef INT64_FORCE_EMULATED */
 
 #ifdef INT64_NATIVE
 
diff --git a/src/include/UInt64.h b/src/include/UInt64.h
index a2b2053..51cc30c 100644
--- a/src/include/UInt64.h
+++ b/src/include/UInt64.h
@@ -25,7 +25,7 @@
 #define CYTOPLASM_UINT64_H
 
 /***
- * @Nm Int64
+ * @Nm UInt64
  * @Nd Fixed-width 64 bit integers.
  * @Dd August 11, 2023
  *
@@ -68,9 +68,9 @@
 
 #include <stddef.h>
 
-#define BIT64_MAX 18446744073709551615UL
+#ifndef INT64_FORCE_EMULATED
 
-/* TODO: Implement signed arithmetic */
+#define BIT64_MAX 18446744073709551615UL
 
 #if UINT_MAX == BIT64_MAX
 /* typedef signed int Int64; */
@@ -86,6 +86,8 @@ typedef unsigned long UInt64;
 
 #endif
 
+#endif /* ifndef INT64_FORCE_EMULATED */
+
 #ifdef UINT64_NATIVE
 
 #define UInt64Create(high, low) (((UInt64) (high) << 32) | (low))
@@ -209,6 +211,7 @@ extern UInt64 UInt64Not(UInt64);
 /**
  * Perform a comparison of the provided 64 bit integers and return a C
  * boolean that is true if and only if they are equal.
+ */
 extern int UInt64Eq(UInt64, UInt64);
 
 /**