diff --git a/021.calling_c/c_code.c b/021.calling_c/c_code.c
index 79657c0..8b42c58 100644
--- a/021.calling_c/c_code.c
+++ b/021.calling_c/c_code.c
@@ -1,3 +1,8 @@
+typedef union {
+  unsigned char* ptr;
+  unsigned short word[2];
+} word_extract_t;
+
 void 
 PokeBitplanePointers(unsigned short* copper, unsigned char* bitplanes, unsigned offset, unsigned numBitplanes, unsigned screenWidthBytes)
 {
@@ -5,8 +10,10 @@ PokeBitplanePointers(unsigned short* copper, unsigned char* bitplanes, unsigned
   copper += offset;
 
   for (i = 0; i < numBitplanes; i++) {
-    *(copper+1) = (unsigned)bitplanes;
-    *(copper+3) = ((unsigned)bitplanes >> 16);
+    word_extract_t extract;
+    extract.ptr = bitplanes;
+    *(copper+1) = extract.word[1];
+    *(copper+3) = extract.word[0];
     bitplanes += screenWidthBytes;
     copper += 4;
   }