diff --git a/build/pkgs/giac/spkg-install b/build/pkgs/giac/spkg-install
index bdd8df6cb8..3fd7a3ef8a 100644
--- a/build/pkgs/giac/spkg-install
+++ b/build/pkgs/giac/spkg-install
@@ -2,6 +2,15 @@
 ## Giac
 ###########################################
 
+# Fix hardcoded paths, while making sure to only update timestamps of actually
+# changed files (otherwise confuses make)
+grep -rlF '/bin/cp' . | while read file
+do
+	sed -e 's@/bin/cp@cp@g' -i "$file"
+done
+
+# Fix input parser syntax
+sed -e 's@yylex (&yylval)@yylex (\&yyval, scanner)@gp' -i 'src/src/input_parser.cc'
 
 if [ "$SAGE_LOCAL" = "" ]; then
    echo "SAGE_LOCAL undefined ... exiting";