diff --git a/ports/bare-arm/lib.c b/ports/bare-arm/lib.c
index 61d3be64e3..1574d5c902 100644
--- a/ports/bare-arm/lib.c
+++ b/ports/bare-arm/lib.c
@@ -110,8 +110,9 @@ char *strchr(const char *s, int c) {
 }
 
 int strncmp(const char *s1, const char *s2, size_t n) {
-    while (*s1 && *s2 && n-- > 0) {
+    while (n > 0 && *s1 && *s2) {
         int c = *s1++ - *s2++;
+        --n;
         if (c) {
             return c;
         }
diff --git a/shared/libc/string0.c b/shared/libc/string0.c
index a3b268e441..3909f70ed8 100644
--- a/shared/libc/string0.c
+++ b/shared/libc/string0.c
@@ -154,7 +154,7 @@ int strcmp(const char *s1, const char *s2) {
 }
 
 int strncmp(const char *s1, const char *s2, size_t n) {
-    while (*s1 && *s2 && n > 0) {
+    while (n > 0 && *s1 && *s2) {
         char c1 = *s1++; // XXX UTF8 get char, next char
         char c2 = *s2++; // XXX UTF8 get char, next char
         n--;