diff --git a/kimgio/webp.cpp b/kimgio/webp.cpp
index d14019a2..a9b916f0 100644
--- a/kimgio/webp.cpp
+++ b/kimgio/webp.cpp
@@ -29,7 +29,7 @@ License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 #include <webp/encode.h>
 #include <webp/demux.h>
 
-static const int s_peekbuffsize = 32;
+static const ushort s_peekbuffsize = 32;
 
 WebPHandler::WebPHandler()
     : m_quality(100),
diff --git a/kutils/karchive/kcompressor.cpp b/kutils/karchive/kcompressor.cpp
index 98114846..04feed03 100644
--- a/kutils/karchive/kcompressor.cpp
+++ b/kutils/karchive/kcompressor.cpp
@@ -32,6 +32,9 @@
 #  include <lzma.h>
 #endif
 
+// space for headers in the worst case scenario
+static const ushort s_headersize = 256;
+
 // for reference:
 // http://linux.math.tifr.res.in/manuals/html/manual_3.html
 
@@ -216,7 +219,7 @@ bool KCompressor::process(const QByteArray &data)
         }
 #if defined(HAVE_BZIP2)
         case KCompressor::TypeBZip2: {
-            d->m_result.resize(data.size() + QT_BUFFSIZE);
+            d->m_result.resize(data.size() + s_headersize);
             uint compsize = d->m_result.size();
 
             const int compresult = BZ2_bzBuffToBuffCompress(
@@ -237,7 +240,7 @@ bool KCompressor::process(const QByteArray &data)
 #endif // HAVE_BZIP2
 #if defined(HAVE_LIBLZMA)
         case KCompressor::TypeXZ: {
-            d->m_result.resize(data.size() + QT_BUFFSIZE);
+            d->m_result.resize(data.size() + s_headersize);
             size_t compsize = d->m_result.size();
 
             lzma_stream comp = LZMA_STREAM_INIT;