diff --git a/Libraries/LibC/ctype.h b/Libraries/LibC/ctype.h
index de88a12354..740832f162 100644
--- a/Libraries/LibC/ctype.h
+++ b/Libraries/LibC/ctype.h
@@ -45,6 +45,18 @@ extern const char _ctype_[256];
 
 int tolower(int);
 int toupper(int);
+int isalnum(int);
+int isalpha(int);
+int iscntrl(int);
+int isdigit(int);
+int isxdigit(int);
+int isspace(int);
+int ispunct(int);
+int isprint(int);
+int isgraph(int);
+int islower(int);
+int isupper(int);
+int isblank(int);
 
 #define isalnum(c) (_ctype_[(int)(c)] & (_U | _L | _N))
 #define isalpha(c) (_ctype_[(int)(c)] & (_U | _L))