diff --git a/src/compress.c b/src/compress.c
index a02ec84..fea4413 100644
--- a/src/compress.c
+++ b/src/compress.c
@@ -188,8 +188,8 @@ PLL_EXPORT unsigned int * pll_compress_site_patterns(char ** sequence,
   }
 
   /* allocate memory for the alignment */
-  memptr = column[0] = (char *)malloc((size_t)((*length)+1) *
-                                      (size_t)count *
+  memptr = column[0] = (char *)malloc((size_t)(*length) *
+                                      (size_t)(count+1) *
                                       sizeof(char));
   if (!memptr)
   {