diff --git a/lib/posix/setenv.c b/lib/posix/setenv.c
index 1660f3fa..a5ee8ff8 100644
--- a/lib/posix/setenv.c
+++ b/lib/posix/setenv.c
@@ -22,25 +22,34 @@
 #include <string.h>
 #include <stdlib.h>
 
+// CONSTANT M2_PTR_SIZE 4
+#define M2_PTR_SIZE 1
+
 int
 setenv (char const *s, char const *v, int overwrite_p)
 {
   char **p = environ;
   int length = strlen (s);
-  while (*p)
+
+  while (p[0] != 0)
     {
-      if (!strncmp (s, *p, length) && *(*p + length) == '=')
-        break;
-      p++;
+      if (strncmp (s, p[0], length) == 0)
+        {
+          char *q = p[0] + length;
+          if (q[0] == '=')
+            break;
+        }
+      p = p + M2_PTR_SIZE;
     }
   char *entry = malloc (length + strlen (v) + 2);
-  int end_p = *p == 0;
-  *p = entry;
+  int end_p = p[0] == 0;
+  p[0] = entry;
   strcpy (entry, s);
   strcpy (entry + length, "=");
   strcpy (entry + length + 1, v);
-  *(entry + length + strlen (v) + 2) = 0;
-  if (end_p)
-    *++p = 0;
+  entry[length + strlen (v) + 2] = 0;
+  if (end_p != 0)
+    p[1] = 0;
+
   return 0;
 }