diff --git a/stix/kernel/Stix.st b/stix/kernel/Stix.st
index f8d49be..2735792 100644
--- a/stix/kernel/Stix.st
+++ b/stix/kernel/Stix.st
@@ -116,7 +116,8 @@
 
 	#method bitAt: index
 	{
-		"## index 1 - least significant bit"
+		"## index is 1-based"
+		<primitive: #_integer_bitat>
 		^(self bitShift: (index - 1) negated) bitAnd: 1.
 	}
 
diff --git a/stix/kernel/test-005.st b/stix/kernel/test-005.st
index 39672ab..12f554c 100644
--- a/stix/kernel/test-005.st
+++ b/stix/kernel/test-005.st
@@ -378,7 +378,7 @@ PROCESS TESTING
 ((-2r1000000000000000000000000000100000000000000000000000000000000000000000000000 bitShift: 13) printStringRadix: 2) dump.
 ((2r1000000000000000000000000000100000000000000000000000000000000000000000000000 bitShift: 13) printStringRadix: 2) dump.
 
-((-2r1111 bitAt: 6) printStringRadix: 2) dump.
+((-2r10 bitAt: 1) printStringRadix: 2) dump.
 
 "
 		FFI isNil dump.
diff --git a/stix/lib/bigint.c b/stix/lib/bigint.c
index 722e0e0..db03745 100644
--- a/stix/lib/bigint.c
+++ b/stix/lib/bigint.c
@@ -1592,6 +1592,23 @@ stix_oop_t stix_bitatint (stix_t* stix, stix_oop_t x, stix_oop_t y)
 {
 	if (STIX_OOP_IS_SMOOI(x) && STIX_OOP_IS_SMOOI(y))
 	{
+		stix_ooi_t v1, v2, v3;
+
+		v1 = STIX_OOP_TO_SMOOI(x);
+		v2 = STIX_OOP_TO_SMOOI(y);
+
+		if (v2 <= 0) return STIX_SMOOI_TO_OOP(0);
+		if (v1 >= 0)
+		{
+			if (v2 >= XXXXXXXXXX) return STIX_SMOOI_TO_OOP(0);
+			v3 = ((stix_oow_t)v1 >> (v2 - 1)) & 1;
+		}
+		else
+		{
+			if (v2 >= XXXXXXXXXX) return STIX_SMOOI_TO_OOP(-1);
+			v3 = ((~(stix_oow_t)-v1 + 1) >> (v2 - 1)) & 1;
+		}
+		return STIX_SMOOI_TO_OOP(v3);
 	}
 	else
 	{
diff --git a/stix/lib/exec.c b/stix/lib/exec.c
index b177d49..9a32b14 100644
--- a/stix/lib/exec.c
+++ b/stix/lib/exec.c
@@ -1208,7 +1208,7 @@ static int prim_integer_bitat (stix_t* stix, stix_ooi_t nargs)
 {
 	stix_oop_t rcv, arg, res;
 
-	STIX_ASSERT (nargs == 2);
+	STIX_ASSERT (nargs == 1);
 
 	rcv = ACTIVE_STACK_GET(stix, stix->sp - 1);
 	arg = ACTIVE_STACK_GET(stix, stix->sp);
diff --git a/stix/lib/stix-cmn.h b/stix/lib/stix-cmn.h
index 9eb3ead..697ffea 100644
--- a/stix/lib/stix-cmn.h
+++ b/stix/lib/stix-cmn.h
@@ -58,11 +58,6 @@
 #endif
 
 
-#if STIX_SIZEOF___INT128_T > 0
-#	undef STIX_SIZEOF___INT128_T
-#	define STIX_SIZEOF___INT128_T 0
-#endif
-
 /* =========================================================================
  * PRIMITIVE TYPE DEFINTIONS
  * ========================================================================= */