diff --git a/OfficeUtils/OfficeUtils.pri b/OfficeUtils/OfficeUtils.pri
index b4e1f497a8..6d99014ddd 100644
--- a/OfficeUtils/OfficeUtils.pri
+++ b/OfficeUtils/OfficeUtils.pri
@@ -1,5 +1,6 @@
 core_linux {
     QMAKE_CXXFLAGS += -Wall -Wno-ignored-qualifiers
+    QMAKE_CFLAGS += -DSTDC
 }
 core_mac {
     QMAKE_CXXFLAGS += -Wall -Wno-ignored-qualifiers
diff --git a/OfficeUtils/src/zlib-1.2.11/gzguts.h b/OfficeUtils/src/zlib-1.2.11/gzguts.h
index 990a4d2514..aefbbd8879 100644
--- a/OfficeUtils/src/zlib-1.2.11/gzguts.h
+++ b/OfficeUtils/src/zlib-1.2.11/gzguts.h
@@ -24,6 +24,7 @@
 #  include <string.h>
 #  include <stdlib.h>
 #  include <limits.h>
+#  include <unistd.h>
 #endif
 
 #ifndef _POSIX_SOURCE