diff --git a/pdf2htmlEX.1.in b/pdf2htmlEX.1.in
index 663c314..e84d668 100644
--- a/pdf2htmlEX.1.in
+++ b/pdf2htmlEX.1.in
@@ -48,7 +48,7 @@ Specify the first page to process
 Specify the last page to process
 .TP
 .B --zoom <ratio>, --fit-width <width>, --fit-height <height>
---zoom specifies the zoom factor directly, --fit-width/height specifies the maximum width/height of a page.
+--zoom specifies the zoom factor directly; --fit-width/height specifies the maximum width/height of a page, the values are in pixels.
 
 If multiple values are specified, the minimum one will be used.
 
diff --git a/src/HTMLRenderer/general.cc b/src/HTMLRenderer/general.cc
index 49b9c26..ffd3602 100644
--- a/src/HTMLRenderer/general.cc
+++ b/src/HTMLRenderer/general.cc
@@ -29,6 +29,7 @@ using std::ostream;
 using std::max;
 using std::min_element;
 using std::vector;
+using std::abs;
 
 static void dummy(void *, enum ErrorCategory, int pos, char *)
 {