diff --git a/Libraries/LibC/ctype.cpp b/Libraries/LibC/ctype.cpp
index f4d35d5e9b..6c76586b1c 100644
--- a/Libraries/LibC/ctype.cpp
+++ b/Libraries/LibC/ctype.cpp
@@ -31,7 +31,7 @@ extern "C" {
 
 const char _ctype_[256] = {
     _C, _C, _C, _C, _C, _C, _C, _C,
-    _C, _C | _S, _C | _S, _C | _S, _C | _S, _C | _S, _C, _C,
+    _C, (char)(_C | _S | _B), _C | _S, _C | _S, _C | _S, _C | _S, _C, _C,
     _C, _C, _C, _C, _C, _C, _C, _C,
     _C, _C, _C, _C, _C, _C, _C, _C,
     (char)(_S | _B), _P, _P, _P, _P, _P, _P, _P,
diff --git a/Libraries/LibC/ctype.h b/Libraries/LibC/ctype.h
index 49d1b05019..740832f162 100644
--- a/Libraries/LibC/ctype.h
+++ b/Libraries/LibC/ctype.h
@@ -56,6 +56,7 @@ 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))
@@ -68,6 +69,7 @@ int isupper(int);
 #define isgraph(c) (_ctype_[(int)(c)] & (_P | _U | _L | _N))
 #define islower(c) ((_ctype_[(int)(c)] & (_U | _L)) == _L)
 #define isupper(c) ((_ctype_[(int)(c)] & (_U | _L)) == _U)
+#define isblank(c) ((_ctype_[(int)(c)] & (_B)))
 
 #define isascii(c) ((unsigned)c <= 127)
 #define toascii(c) ((c)&127)