diff --git a/py/nlrx64.c b/py/nlrx64.c
index c23fd8fc6a..aeaacd50c5 100644
--- a/py/nlrx64.c
+++ b/py/nlrx64.c
@@ -34,7 +34,11 @@
 // x86-64 callee-save registers are:
 //  rbx, rbp, rsp, r12, r13, r14, r15
 
-#define NLR_OS_WINDOWS (defined(_WIN32) || defined(__CYGWIN__))
+#if defined(_WIN32) || defined(__CYGWIN__)
+#define NLR_OS_WINDOWS 1
+#else
+#define NLR_OS_WINDOWS 0
+#endif
 
 __attribute__((used)) unsigned int nlr_push_tail(nlr_buf_t *nlr);
 
diff --git a/py/nlrx86.c b/py/nlrx86.c
index 58aaa1a571..8d15d7bab9 100644
--- a/py/nlrx86.c
+++ b/py/nlrx86.c
@@ -35,7 +35,11 @@
 // For reference, x86 callee save regs are:
 //  ebx, esi, edi, ebp, esp, eip
 
-#define NLR_OS_WINDOWS (defined(_WIN32) || defined(__CYGWIN__))
+#if defined(_WIN32) || defined(__CYGWIN__)
+#define NLR_OS_WINDOWS 1
+#else
+#define NLR_OS_WINDOWS 0
+#endif
 
 #if NLR_OS_WINDOWS
 unsigned int nlr_push_tail(nlr_buf_t *nlr) asm("nlr_push_tail");