diff --git a/src/ucore_bcd.c b/src/ucore_bcd.c
index 9a202d9..3dd978c 100644
--- a/src/ucore_bcd.c
+++ b/src/ucore_bcd.c
@@ -16,14 +16,14 @@ uc_ascii2bcd(const char *ascii, unsigned char *bcdout, unsigned char filler)
             continue;
         }
 
-        *bcdp |= (*ascii - '0') << shift;
-
         if (shift) {
+            *bcdp |= (*ascii - '0') << 4;
             bcdp++;
-            *bcdp = 0;
+        } else {
+            *bcdp = (*ascii - '0');
         }
 
-        shift = 4 - shift;
+        shift = !shift;
     }
 
     if (shift) {