diff --git a/source/core_http_client.c b/source/core_http_client.c
index 996dc5af..11b4ac27 100644
--- a/source/core_http_client.c
+++ b/source/core_http_client.c
@@ -1360,18 +1360,18 @@ static HTTPStatus_t addHeader( HTTPRequestHeaders_t * pRequestHeaders,
     assert( fieldLen != 0U );
     assert( valueLen != 0U );
 
-    pBufferCur = ( char * ) ( pRequestHeaders->pBuffer + pRequestHeaders->headersLen );
+    pBufferCur = ( char * ) &( pRequestHeaders->pBuffer[ pRequestHeaders->headersLen ] );
     backtrackHeaderLen = pRequestHeaders->headersLen;
 
     /* Backtrack before trailing "\r\n" (HTTP header end) if it's already written.
      * Note that this method also writes trailing "\r\n" before returning.
      * The first condition prevents reading before start of the header. */
     if( ( HTTP_HEADER_END_INDICATOR_LEN <= pRequestHeaders->headersLen ) &&
-        ( strncmp( ( char * ) pBufferCur - HTTP_HEADER_END_INDICATOR_LEN,
+        ( strncmp( ( char * ) &pBufferCur[ 0U - HTTP_HEADER_END_INDICATOR_LEN ],
                    HTTP_HEADER_END_INDICATOR, HTTP_HEADER_END_INDICATOR_LEN ) == 0 ) )
     {
         backtrackHeaderLen -= HTTP_HEADER_LINE_SEPARATOR_LEN;
-        pBufferCur -= HTTP_HEADER_LINE_SEPARATOR_LEN;
+        pBufferCur = &pBufferCur[ 0U - HTTP_HEADER_LINE_SEPARATOR_LEN ];
     }
 
     /* Check if there is enough space in buffer for additional header. */