diff --git a/renderdoc/os/posix/ggp/ggp_stringio.cpp b/renderdoc/os/posix/ggp/ggp_stringio.cpp
index d3203e13d..a9411adb0 100644
--- a/renderdoc/os/posix/ggp/ggp_stringio.cpp
+++ b/renderdoc/os/posix/ggp/ggp_stringio.cpp
@@ -22,6 +22,7 @@
  * THE SOFTWARE.
  ******************************************************************************/
 
+#include <ctype.h>
 #include <dlfcn.h>
 #include <errno.h>
 #include <iconv.h>