diff --git a/reactos/lib/dbghelp/module.c b/reactos/lib/dbghelp/module.c
index ea5a955d93f..4df3bd35460 100644
--- a/reactos/lib/dbghelp/module.c
+++ b/reactos/lib/dbghelp/module.c
@@ -22,6 +22,7 @@
 #include "config.h"
 #include <stdlib.h>
 #include <stdio.h>
+#include <ctype.h>
 #include <string.h>
 #include <assert.h>
 
diff --git a/reactos/lib/dbghelp/path.c b/reactos/lib/dbghelp/path.c
index 604998fde3e..08238d3ebbe 100644
--- a/reactos/lib/dbghelp/path.c
+++ b/reactos/lib/dbghelp/path.c
@@ -21,6 +21,7 @@
 #include "config.h"
 #include <stdlib.h>
 #include <stdio.h>
+#include <ctype.h>
 #include <string.h>
 
 #include "dbghelp_private.h"
diff --git a/reactos/lib/dbghelp/stabs.c b/reactos/lib/dbghelp/stabs.c
index 0104fdd9829..368ec0138b9 100644
--- a/reactos/lib/dbghelp/stabs.c
+++ b/reactos/lib/dbghelp/stabs.c
@@ -39,6 +39,7 @@
 #endif
 #include <limits.h>
 #include <stdlib.h>
+#include <ctype.h>
 #include <string.h>
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>