diff --git a/src/console/vtxprintf.c b/src/console/vtxprintf.c
index c429ac79e2..01091c82e8 100644
--- a/src/console/vtxprintf.c
+++ b/src/console/vtxprintf.c
@@ -16,6 +16,7 @@
  */
 
 #include <console/vtxprintf.h>
+#include <ctype.h>
 #include <string.h>
 
 #define call_tx(x) tx_byte(x, data)
diff --git a/src/include/ctype.h b/src/include/ctype.h
new file mode 100644
index 0000000000..b4684af768
--- /dev/null
+++ b/src/include/ctype.h
@@ -0,0 +1,56 @@
+#ifndef CTYPE_H
+#define CTYPE_H
+
+static inline int isspace(int c)
+{
+	switch (c) {
+	case ' ': case '\f': case '\n':
+	case '\r': case '\t': case '\v':
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+static inline int isprint(int c)
+{
+	return c >= ' ' && c <= '~';
+}
+
+static inline int isdigit(int c)
+{
+	return (c >= '0' && c <= '9');
+}
+
+static inline int isxdigit(int c)
+{
+	return ((c >= '0' && c <= '9') ||
+		(c >= 'a' && c <= 'f') ||
+		(c >= 'A' && c <= 'F'));
+}
+
+static inline int isupper(int c)
+{
+	return (c >= 'A' && c <= 'Z');
+}
+
+static inline int islower(int c)
+{
+	return (c >= 'a' && c <= 'z');
+}
+
+static inline int toupper(int c)
+{
+	if (islower(c))
+		c -= 'a'-'A';
+	return c;
+}
+
+static inline int tolower(int c)
+{
+	if (isupper(c))
+		c -= 'A'-'a';
+	return c;
+}
+
+#endif /* CTYPE_H */
diff --git a/src/include/string.h b/src/include/string.h
index d164f32b83..30241303eb 100644
--- a/src/include/string.h
+++ b/src/include/string.h
@@ -50,56 +50,4 @@ char *strrchr(const char *s, int c);
  */
 unsigned int skip_atoi(char **s);
 
-static inline int isspace(int c)
-{
-	switch (c) {
-	case ' ': case '\f': case '\n':
-	case '\r': case '\t': case '\v':
-		return 1;
-	default:
-		return 0;
-	}
-}
-
-static inline int isprint(int c)
-{
-	return c >= ' ' && c <= '~';
-}
-
-static inline int isdigit(int c)
-{
-	return (c >= '0' && c <= '9');
-}
-
-static inline int isxdigit(int c)
-{
-	return ((c >= '0' && c <= '9') ||
-		(c >= 'a' && c <= 'f') ||
-		(c >= 'A' && c <= 'F'));
-}
-
-static inline int isupper(int c)
-{
-	return (c >= 'A' && c <= 'Z');
-}
-
-static inline int islower(int c)
-{
-	return (c >= 'a' && c <= 'z');
-}
-
-static inline int toupper(int c)
-{
-	if (islower(c))
-		c -= 'a'-'A';
-	return c;
-}
-
-static inline int tolower(int c)
-{
-	if (isupper(c))
-		c -= 'A'-'a';
-	return c;
-}
-
 #endif /* STRING_H */
diff --git a/src/lib/device_tree.c b/src/lib/device_tree.c
index 2e81a08779..b8faab53b8 100644
--- a/src/lib/device_tree.c
+++ b/src/lib/device_tree.c
@@ -18,6 +18,7 @@
 #include <assert.h>
 #include <commonlib/stdlib.h>
 #include <console/console.h>
+#include <ctype.h>
 #include <device_tree.h>
 #include <endian.h>
 #include <stdint.h>
diff --git a/src/lib/edid.c b/src/lib/edid.c
index 3087172952..e2f213c5b0 100644
--- a/src/lib/edid.c
+++ b/src/lib/edid.c
@@ -31,6 +31,7 @@
 #include <assert.h>
 #include <stddef.h>
 #include <console/console.h>
+#include <ctype.h>
 #include <stdint.h>
 #include <string.h>
 #include <stdlib.h>
diff --git a/src/lib/fit.c b/src/lib/fit.c
index 045f52f408..f1052e8f23 100644
--- a/src/lib/fit.c
+++ b/src/lib/fit.c
@@ -17,6 +17,7 @@
 
 #include <assert.h>
 #include <console/console.h>
+#include <ctype.h>
 #include <endian.h>
 #include <stdint.h>
 #include <bootmem.h>
diff --git a/src/lib/hexdump.c b/src/lib/hexdump.c
index ca36ddee0e..1e689e3e53 100644
--- a/src/lib/hexdump.c
+++ b/src/lib/hexdump.c
@@ -13,6 +13,7 @@
  */
 
 #include <console/console.h>
+#include <ctype.h>
 #include <lib.h>
 #include <string.h>
 
diff --git a/src/lib/hexstrtobin.c b/src/lib/hexstrtobin.c
index ed2abc4e8b..61290b86d3 100644
--- a/src/lib/hexstrtobin.c
+++ b/src/lib/hexstrtobin.c
@@ -11,6 +11,7 @@
  * GNU General Public License for more details.
  */
 
+#include <ctype.h>
 #include <lib.h>
 #include <string.h>
 
diff --git a/src/lib/string.c b/src/lib/string.c
index a19f017852..eb6adb67c7 100644
--- a/src/lib/string.c
+++ b/src/lib/string.c
@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <ctype.h>
 #include <rules.h>
 #include <string.h>
 #include <stddef.h>
diff --git a/src/vendorcode/cavium/bdk/lame_string.c b/src/vendorcode/cavium/bdk/lame_string.c
index 11c5add209..3906ca5904 100644
--- a/src/vendorcode/cavium/bdk/lame_string.c
+++ b/src/vendorcode/cavium/bdk/lame_string.c
@@ -11,6 +11,7 @@
  */
 
 #include <assert.h>
+#include <ctype.h>
 #include <string.h>
 #include <lame_string.h>
 
diff --git a/src/vendorcode/cavium/bdk/libdram/dram-spd.c b/src/vendorcode/cavium/bdk/libdram/dram-spd.c
index 1296119b65..84df69a923 100644
--- a/src/vendorcode/cavium/bdk/libdram/dram-spd.c
+++ b/src/vendorcode/cavium/bdk/libdram/dram-spd.c
@@ -44,6 +44,7 @@
 #include <libbdk-hal/bdk-config.h>
 #include <libbdk-hal/bdk-twsi.h>
 #include <assert.h>
+#include <ctype.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/src/vendorcode/google/chromeos/vpd_mac.c b/src/vendorcode/google/chromeos/vpd_mac.c
index e3ef04b669..fcd3efec9e 100644
--- a/src/vendorcode/google/chromeos/vpd_mac.c
+++ b/src/vendorcode/google/chromeos/vpd_mac.c
@@ -15,6 +15,7 @@
 
 #include <boot/coreboot_tables.h>
 #include <console/console.h>
+#include <ctype.h>
 #include <string.h>
 
 #include <drivers/vpd/vpd.h>