diff --git a/asm_unpackers/Makefile b/asm_unpackers/Makefile
index 40c959e..43b7473 100644
--- a/asm_unpackers/Makefile
+++ b/asm_unpackers/Makefile
@@ -17,6 +17,14 @@ test_armv6m: build/unpack_armv6m
 build/unpack_armv6m.bin: unpack_armv6m.S
 	arm-none-eabi-gcc -march=armv6-m -c -o build/unpack_armv6m.o $?
 	arm-none-eabi-objcopy -O binary --only-section=.text build/unpack_armv6m.o $@
+	
+build/unpack_c: ../c_unpacker/main.c ../c_unpacker/unpack.c
+	mkdir -p build
+	gcc -g -o $@ $^
+
+test_c: build/unpack_c
+	$< test_data.upk /tmp/out.bin
+	cmp test_data.bin /tmp/out.bin
 
 sizes: build/unpack_armv6m.bin
 	ls -l build/*.bin
\ No newline at end of file
diff --git a/c_unpacker/decode_bit_alt.c b/c_unpacker/decode_bit_alt.c
new file mode 100644
index 0000000..2003cdd
--- /dev/null
+++ b/c_unpacker/decode_bit_alt.c
@@ -0,0 +1,33 @@
+int upkr_decode_bit(int context_index) {
+#ifdef UPKR_BITSTREAM
+    while(upkr_state < 32768) {
+        if(upkr_bits_left == 0) {
+            upkr_current_byte = *upkr_data_ptr++;
+            upkr_bits_left = 8;
+        }
+        upkr_state = (upkr_state << 1) + (upkr_current_byte & 1);
+        upkr_current_byte >>= 1;
+        --upkr_bits_left;
+    }
+#else
+    while(upkr_state < 4096) {
+        upkr_state = (upkr_state << 8) | *upkr_data_ptr++;
+    }
+#endif
+   
+    int prob = upkr_probs[context_index];
+    int bit = (upkr_state & 255) < prob ? 1 : 0;
+    
+    if(bit) {
+        prob = 256 - prob;
+    }
+    upkr_state -= prob * ((upkr_state >> 8) + (bit ^ 1));
+    prob -= (prob + 8) >> 4;
+    if(bit) {
+        prob = -prob;
+    }
+    upkr_probs[context_index] = prob;
+
+    return bit;
+}
+
diff --git a/c_unpacker/unpack.c b/c_unpacker/unpack.c
index 0b79206..d317e02 100644
--- a/c_unpacker/unpack.c
+++ b/c_unpacker/unpack.c
@@ -32,17 +32,14 @@ int upkr_decode_bit(int context_index) {
     int prob = upkr_probs[context_index];
     int bit = (upkr_state & 255) < prob ? 1 : 0;
     
-    int tmp = prob;
-    if(!bit) {
-        tmp = 256 - tmp;
+    if(bit) {
+        upkr_state = prob * (upkr_state >> 8) + (upkr_state & 255);
+        prob += (256 - prob + 8) >> 4;
+    } else {
+        upkr_state = (256 - prob) * (upkr_state >> 8) + (upkr_state & 255) - prob;
+        prob -= (prob + 8) >> 4;
     }
-    upkr_state = tmp * (upkr_state >> 8) + (upkr_state & 255);
-    tmp += (256 - tmp + 8) >> 4;
-    if(!bit) {
-        upkr_state -= prob;
-        tmp = 256 - tmp;
-    }
-    upkr_probs[context_index] = tmp;
+    upkr_probs[context_index] = prob;
 
     return bit;
 }