Index: lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -110,6 +110,9 @@
 #define times __times13
 #define wait3 __wait350
 #define wait4 __wait450
+extern const unsigned short *_ctype_tab_;
+extern const short *_toupper_tab_;
+extern const short *_tolower_tab_;
 #endif
 
 // Platform-specific options.
@@ -3186,13 +3189,25 @@
 #endif
 
 #if SANITIZER_INTERCEPT_SETLOCALE
+static void unpoison_ctype_arrays(void *ctx) {
+#if SANITIZER_NETBSD
+  // These arrays contain 256 regular elements in unsigned char range + 1 EOF
+  COMMON_INTERCEPTOR_WRITE_RANGE(ctx, _ctype_tab_, 257 * sizeof(short));
+  COMMON_INTERCEPTOR_WRITE_RANGE(ctx, _toupper_tab_, 257 * sizeof(short));
+  COMMON_INTERCEPTOR_WRITE_RANGE(ctx, _tolower_tab_, 257 * sizeof(short));
+#endif
+}
+
 INTERCEPTOR(char *, setlocale, int category, char *locale) {
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, setlocale, category, locale);
   if (locale)
     COMMON_INTERCEPTOR_READ_RANGE(ctx, locale, REAL(strlen)(locale) + 1);
   char *res = REAL(setlocale)(category, locale);
-  if (res) COMMON_INTERCEPTOR_WRITE_RANGE(ctx, res, REAL(strlen)(res) + 1);
+  if (res) {
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, res, REAL(strlen)(res) + 1);
+    unpoison_ctype_arrays(ctx);
+  }
   return res;
 }
 
Index: test/sanitizer_common/TestCases/ctype.c
===================================================================
--- test/sanitizer_common/TestCases/ctype.c
+++ test/sanitizer_common/TestCases/ctype.c
@@ -0,0 +1,89 @@
+// RUN: %clang %s -o %t && %run %t 2>&1 | FileCheck %s
+
+#include <ctype.h>
+#include <limits.h>
+#include <locale.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void check_ctype(void) {
+  unsigned char c;
+  volatile size_t i = 0; /* a dummy variable to prevent optimizing code out */
+
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isalpha(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isascii(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isblank(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!iscntrl(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isdigit(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isgraph(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!islower(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isprint(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!ispunct(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isspace(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isupper(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isxdigit(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!isalnum(c);
+
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!tolower(c);
+  for (c = 0; c < UCHAR_MAX; c++)
+    i += !!toupper(c);
+
+  i += !!isalpha(EOF);
+  i += !!isascii(EOF);
+  i += !!isblank(EOF);
+  i += !!iscntrl(EOF);
+  i += !!isdigit(EOF);
+  i += !!isgraph(EOF);
+  i += !!islower(EOF);
+  i += !!isprint(EOF);
+  i += !!ispunct(EOF);
+  i += !!isspace(EOF);
+  i += !!isupper(EOF);
+  i += !!isxdigit(EOF);
+  i += !!isalnum(EOF);
+
+  i += !!tolower(EOF);
+  i += !!toupper(EOF);
+
+  if (i)
+    return;
+  else
+    return;
+}
+
+int main(int argc, char **argv) {
+  check_ctype();
+
+  setlocale(LC_ALL, "");
+
+  check_ctype();
+
+  setlocale(LC_ALL, "en_US.UTF-8");
+
+  check_ctype();
+
+  setlocale(LC_CTYPE, "pl_PL.UTF-8");
+
+  check_ctype();
+
+  printf("OK\n");
+
+  // CHECK: OK
+
+  return 0;
+}