diff --git a/src/datatype/dt_pack.c b/src/datatype/dt_pack.c
index 0b79f69968..ee8aff85bb 100644
--- a/src/datatype/dt_pack.c
+++ b/src/datatype/dt_pack.c
@@ -294,19 +294,24 @@ int lam_convertor_pack( lam_convertor_t* pConv, struct iovec* out, unsigned int
     if( pData->flags & DT_FLAG_CONTIGUOUS ) {
         if( pData->size == (extent = (pData->ub - pData->lb)) ) {
             size_t length = pData->size * pConv->count;
+            char* pSrc = pConv->pBaseBuf + pData->true_lb + pConv->bConverted;
+
             if( out[0].iov_base == NULL ) {
-                out[0].iov_base = pConv->pBaseBuf + pData->true_lb;
-                if( (out[0].iov_base == 0) ||
-                    ((pConv->bConverted + out[0].iov_len) > length) )
+                out[0].iov_base = pSrc;
+                if( (pConv->bConverted + out[0].iov_len) > length )
                     out[0].iov_len = length - pConv->bConverted;
             } else {
                 /* contiguous data just memcpy the smallest data in the user buffer */
                 out[0].iov_len = IMIN( out[0].iov_len, pData->size * pConv->count );
-                MEMCPY( out[0].iov_base, pConv->pBaseBuf + pData->true_lb, out[0].iov_len);
+                MEMCPY( out[0].iov_base, pSrc, out[0].iov_len);
             }
             pConv->bConverted += out[0].iov_len;
-            return 0;
-        }         
+            return (pConv->bConverted == length);
+        } else {  /* datatype is contiguous but there are gap inbetween elements */
+            if( out[0].iov_base != NULL ) {
+                return -1;
+            }
+        }        
     }
     if( out[0].iov_base == NULL ) {
         out[0].iov_len = pConv->count * pData->size;
diff --git a/src/datatype/dt_unpack.c b/src/datatype/dt_unpack.c
index 43ae668e29..a1891bd0ea 100644
--- a/src/datatype/dt_unpack.c
+++ b/src/datatype/dt_unpack.c
@@ -319,17 +319,15 @@ int lam_convertor_unpack( lam_convertor_t* pConvertor,
     if( pConvertor->flags & DT_FLAG_CONTIGUOUS ) {
         if( pInputv[0].iov_base == NULL ) {
             rc = pConvertor->count * pData->size;
+            pInputv[0].iov_base = pConvertor->pBaseBuf + pData->true_lb + pConvertor->bConverted;
             if( pInputv[0].iov_len == 0 ) {  /* give me the whole buffer */
-                pInputv[0].iov_base = pConvertor->pBaseBuf + pData->true_lb;
-                pInputv[0].iov_len = rc;
-                return 1;
+                pInputv[0].iov_len = rc - pConvertor->bConverted;
             } else {  /* what about the next chunk ? */
-                pInputv[0].iov_base = pConvertor->pBaseBuf + pData->true_lb + pConvertor->bConverted;
                 if( pInputv[0].iov_len > (rc - pConvertor->bConverted) )
                     pInputv[0].iov_len = rc - pConvertor->bConverted;
-                pConvertor->bConverted += pInputv[0].iov_len;
-                return (pConvertor->bConverted == rc);
             }
+            pConvertor->bConverted += pInputv[0].iov_len;
+            return (pConvertor->bConverted == rc);
         }
     }
     if( (pInput >= pOutput) && (pInput < (pOutput + pConvertor->count * (pData->ub - pData->lb))) ) {