diff --git a/BasiliskII/src/Unix/configure.ac b/BasiliskII/src/Unix/configure.ac
index b3b266c3..e831792c 100644
--- a/BasiliskII/src/Unix/configure.ac
+++ b/BasiliskII/src/Unix/configure.ac
@@ -119,22 +119,6 @@ if [[ "x$HAVE_I386" = "xyes" ]]; then
   ])
 fi
 
-dnl Check if we should really be assuming x86_64 even if we detected HAVE_I386 above.
-if [[ "x$HAVE_I386" = "xyes" ]]; then
-  AC_TRY_RUN([
-    int main(void) {
-        #if defined(__x86_64__)
-                return 0;
-        #else
-                return 1;
-        #endif
-    }
-  ], [
-    HAVE_I386=no
-    HAVE_X86_64=yes
-  ])
-fi
-
 dnl Checks for programs.
 AC_PROG_CC
 AC_PROG_CC_C_O
@@ -1012,6 +996,7 @@ AC_CACHE_CHECK([whether your system supports Mach exceptions],
   AC_LANG_SAVE
   AC_LANG_CPLUSPLUS
   AC_TRY_RUN([
+    #define HAVE_UNISTD_H 1
     #define HAVE_MACH_VM 1
     #define HAVE_MACH_TASK_SELF 1
     #define HAVE_MACH_EXCEPTIONS 1
@@ -1356,7 +1341,7 @@ if [[ "x$HAVE_GCC27" = "xyes" -a "x$HAVE_I386" = "xyes" ]]; then
   DEFINES="$DEFINES -DUNALIGNED_PROFITABLE -DREGPARAM=\"__attribute__((regparm(3)))\""
   if [[ "x$HAVE_GAS" = "xyes" ]]; then
     ASM_OPTIMIZATIONS=i386
-    DEFINES="-m32 $DEFINES -DX86_ASSEMBLY -DOPTIMIZED_FLAGS -DSAHF_SETO_PROFITABLE"
+    DEFINES="$DEFINES -DX86_ASSEMBLY -DOPTIMIZED_FLAGS -DSAHF_SETO_PROFITABLE"
     JITSRCS="cpuemu1_nf.cpp cpuemu2_nf.cpp cpuemu3_nf.cpp cpuemu4_nf.cpp cpuemu5_nf.cpp cpuemu6_nf.cpp cpuemu7_nf.cpp cpuemu8_nf.cpp $JITSRCS"
     CAN_JIT=yes
   fi
@@ -1365,7 +1350,7 @@ elif [[ "x$HAVE_GCC30" = "xyes" -a "x$HAVE_X86_64" = "xyes" ]]; then
   DEFINES="$DEFINES -DUNALIGNED_PROFITABLE"
   if [[ "x$HAVE_GAS" = "xyes" ]]; then
     ASM_OPTIMIZATIONS="x86-64"
-    DEFINES="-m64 $DEFINES -DX86_64_ASSEMBLY -DOPTIMIZED_FLAGS"
+    DEFINES="$DEFINES -DX86_64_ASSEMBLY -DOPTIMIZED_FLAGS"
     JITSRCS="cpuemu1_nf.cpp cpuemu2_nf.cpp cpuemu3_nf.cpp cpuemu4_nf.cpp cpuemu5_nf.cpp cpuemu6_nf.cpp cpuemu7_nf.cpp cpuemu8_nf.cpp $JITSRCS"
     CAN_JIT=yes
   fi