diff --git a/c/flisp.c b/c/flisp.c
index ade05ac..327542b 100644
--- a/c/flisp.c
+++ b/c/flisp.c
@@ -47,6 +47,8 @@
 
 #include "scheme.h"
 
+#include "opcodes.h"
+
 #include "../scheme-boot/boot_image.h"
 
 static char *builtin_names[] = {
diff --git a/c/read.h b/c/read.h
index 8a0e2d1..411c966 100644
--- a/c/read.h
+++ b/c/read.h
@@ -132,7 +132,7 @@ int isnumtok_base(char *tok, value_t *pval, int base)
         if (!read_digits(tok + 1, &end, base, &ui64)) {
             return 0;
         }
-        if (ui64 >= 0x8000000000000000ULL) {
+        if (ui64 >= UINT64_TOP_BIT) {
             lerror(ArgError, "Number too negative");
         }
         if (pval)
diff --git a/c/scheme.h b/c/scheme.h
index 154038a..30a5125 100644
--- a/c/scheme.h
+++ b/c/scheme.h
@@ -15,6 +15,10 @@
 //
 // We assume the LP64 convention for 64-bit platforms.
 
+#ifdef __DJGPP__
+#include "scheme_compiler_djgpp.h"
+#endif
+
 #ifdef __DMC__
 #include "scheme_compiler_dmc.h"
 #endif
@@ -31,14 +35,6 @@
 #include "scheme_compiler_watcomc.h"
 #endif
 
-#ifdef BITS64
-#define TOP_BIT 0x8000000000000000
-#define NBITS 64
-#else
-#define TOP_BIT 0x80000000
-#define NBITS 32
-#endif
-
 #define ALIGN(x, sz) (((x) + (sz - 1)) & (-sz))
 
 extern double D_PNAN;
@@ -769,6 +765,12 @@ typedef enum {
 
 #define N_NUMTYPES ((int)T_DOUBLE + 1)
 
+#ifdef BITS64
+#define T_FIXNUM T_INT64
+#else
+#define T_FIXNUM T_INT32
+#endif
+
 value_t relocate_lispvalue(value_t v);
 void print_traverse(value_t v);
 void fl_print_chr(char c, struct ios *f);
@@ -995,6 +997,4 @@ value_t fl_stringp(value_t *args, uint32_t nargs);
 value_t fl_string_reverse(value_t *args, uint32_t nargs);
 value_t fl_string_sub(value_t *args, uint32_t nargs);
 
-#include "opcodes.h"
-
 #include "htableh_inc.h"
diff --git a/c/scheme_compiler_gnuc.h b/c/scheme_compiler_gnuc.h
index 1f43c82..69c4f2e 100644
--- a/c/scheme_compiler_gnuc.h
+++ b/c/scheme_compiler_gnuc.h
@@ -2,12 +2,34 @@ typedef uintptr_t value_t;
 typedef uintptr_t ufixnum_t;
 typedef intptr_t fixnum_t;
 
+#define BITS64
+
 #ifdef BITS64
-#define T_FIXNUM T_INT64
+#define UINT64_TOP_BIT 0x8000000000000000ULL
+#define TOP_BIT UINT64_TOP_BIT
 #else
-#define T_FIXNUM T_INT32
+#define UINT32_TOP_BIT 0x80000000
+#define TOP_BIT UINT32_TOP_BIT
 #endif
 
+#define DBL_MAXINT 9007199254740992LL
+#define FLT_MAXINT 16777216
+#define U64_MAX 18446744073709551615ULL
+#define S64_MAX 9223372036854775807LL
+#define S64_MIN (-S64_MAX - 1LL)
+#define BIT63 0x8000000000000000LL
+#define BIT31 0x80000000
+
+#define LOG2_10 3.3219280948873626
+#define sign_bit(r) ((*(int64_t *)&(r)) & BIT63)
+#define NBABS(n, nb) (((n) ^ ((n) >> ((nb)-1))) - ((n) >> ((nb)-1)))
+#define DFINITE(d) \
+    (((*(int64_t *)&(d)) & 0x7ff0000000000000LL) != 0x7ff0000000000000LL)
+#define DNAN(d) ((d) != (d))
+
+#define __unlikely(x) __builtin_expect(!!(x), 0)
+#define __likely(x) __builtin_expect(!!(x), 1)
+
 void DivideByZeroError(void) __attribute__((__noreturn__));
 
 void lerrorf(value_t e, const char *format, ...)
@@ -22,28 +44,3 @@ __attribute__((__noreturn__));
 
 void bounds_error(const char *fname, value_t arr, value_t ind)
 __attribute__((__noreturn__));
-
-// branch prediction annotations
-#ifdef __GNUC__
-#define __unlikely(x) __builtin_expect(!!(x), 0)
-#define __likely(x) __builtin_expect(!!(x), 1)
-#else
-#define __unlikely(x) (x)
-#define __likely(x) (x)
-#endif
-
-#define DBL_MAXINT 9007199254740992LL
-#define FLT_MAXINT 16777216
-#define U64_MAX 18446744073709551615ULL
-#define S64_MAX 9223372036854775807LL
-#define S64_MIN (-S64_MAX - 1LL)
-#define BIT63 0x8000000000000000LL
-#define BIT31 0x80000000
-
-#define LOG2_10 3.3219280948873626
-#define sign_bit(r) ((*(int64_t *)&(r)) & BIT63)
-#define LABS(n) (((n) ^ ((n) >> (NBITS - 1))) - ((n) >> (NBITS - 1)))
-#define NBABS(n, nb) (((n) ^ ((n) >> ((nb)-1))) - ((n) >> ((nb)-1)))
-#define DFINITE(d) \
-    (((*(int64_t *)&(d)) & 0x7ff0000000000000LL) != 0x7ff0000000000000LL)
-#define DNAN(d) ((d) != (d))
diff --git a/c/scheme_compiler_watcomc.h b/c/scheme_compiler_watcomc.h
index 9d2e2d8..37b9b53 100644
--- a/c/scheme_compiler_watcomc.h
+++ b/c/scheme_compiler_watcomc.h
@@ -1,11 +1,12 @@
-#ifdef __WATCOMC__
-typedef float float_t;
-typedef double double_t;
+#define __unlikely(x) (x)
+#define __likely(x) (x)
+
 #define __ORDER_BIG_ENDIAN__ 4321
 #define __ORDER_LITTLE_ENDIAN__ 1234
 #define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
-#define BITS32
-#endif
+
+typedef float float_t;
+typedef double double_t;
 
 #pragma aux DivideByZeroError aborts;
 extern void DivideByZeroError(void);