diff --git a/Include/pymath.h b/Include/pymath.h
--- a/Include/pymath.h
+++ b/Include/pymath.h
@@ -182,7 +182,7 @@
 #if defined(__FreeBSD__) || defined(__OpenBSD__)
 #define Py_OVERFLOWED(X) isinf(X)
 #else
-#define Py_OVERFLOWED(X) ((X) != 0.0 && (errno == ERANGE ||    \
+#define Py_OVERFLOWED(X) ((X) != 0.0 && (Py_errno == ERANGE || \
 					 (X) == Py_HUGE_VAL || \
 					 (X) == -Py_HUGE_VAL))
 #endif
diff --git a/Include/pyport.h b/Include/pyport.h
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -463,15 +463,15 @@
  *    X is evaluated more than once.
  */
 #if defined(__FreeBSD__) || defined(__OpenBSD__) || (defined(__hpux) && defined(__ia64))
-#define _Py_SET_EDOM_FOR_NAN(X) if (isnan(X)) errno = EDOM;
+#define _Py_SET_EDOM_FOR_NAN(X) if (isnan(X)) Py_errno = EDOM;
 #else
 #define _Py_SET_EDOM_FOR_NAN(X) ;
 #endif
 #define Py_SET_ERRNO_ON_MATH_ERROR(X) \
     do { \
-        if (errno == 0) { \
+        if (Py_errno == 0) { \
             if ((X) == Py_HUGE_VAL || (X) == -Py_HUGE_VAL) \
-                errno = ERANGE; \
+                Py_errno = ERANGE; \
             else _Py_SET_EDOM_FOR_NAN(X) \
         } \
     } while(0)
@@ -497,23 +497,23 @@
  */
 #define Py_ADJUST_ERANGE1(X)                                            \
     do {                                                                \
-        if (errno == 0) {                                               \
+        if (Py_errno == 0) {                                            \
             if ((X) == Py_HUGE_VAL || (X) == -Py_HUGE_VAL)              \
-                errno = ERANGE;                                         \
+                Py_errno = ERANGE;                                      \
         }                                                               \
-        else if (errno == ERANGE && (X) == 0.0)                         \
-            errno = 0;                                                  \
+        else if (Py_errno == ERANGE && (X) == 0.0)                     \
+            Py_errno = 0;                                               \
     } while(0)
 
 #define Py_ADJUST_ERANGE2(X, Y)                                         \
     do {                                                                \
         if ((X) == Py_HUGE_VAL || (X) == -Py_HUGE_VAL ||                \
             (Y) == Py_HUGE_VAL || (Y) == -Py_HUGE_VAL) {                \
-                        if (errno == 0)                                 \
-                                errno = ERANGE;                         \
+                        if (Py_errno == 0)                              \
+                                Py_errno = ERANGE;                      \
         }                                                               \
-        else if (errno == ERANGE)                                       \
-            errno = 0;                                                  \
+        else if (Py_errno == ERANGE)                                    \
+            Py_errno = 0;                                               \
     } while(0)
 
 /*  The functions _Py_dg_strtod and _Py_dg_dtoa in Python/dtoa.c (which are
@@ -868,4 +868,18 @@
 #endif
 #endif
 
+/*
+ * Access to errno variable of Python's C runtime library. When a Python
+ * extension is linked to another CRT (e.g. on Windows with different version
+ * of Visual Studio) it sees another errno as each CRT has its own thread
+ * local storage.
+ */
+PyAPI_FUNC(int *) _Py_errno(void);
+
+#ifdef Py_BUILD_CORE
+#    define Py_errno errno
+#else
+#    define Py_errno (*_Py_errno())
+#endif
+
 #endif /* Py_PYPORT_H */
diff --git a/Python/errors.c b/Python/errors.c
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -977,6 +977,13 @@
     return NULL;
 }
 
+/* access Python core's errno TLS variable */
+int *
+_Py_errno()
+{
+    return &errno;
+}
+
 #ifdef __cplusplus
 }
 #endif