diff --git a/sys/src/ape/lib/ap/gen/putenv.c b/sys/src/ape/lib/ap/gen/putenv.c
new file mode 100644
index 000000000..56a1184ba
--- /dev/null
+++ b/sys/src/ape/lib/ap/gen/putenv.c
@@ -0,0 +1,24 @@
+#include <stdlib.h>
+
+extern	char **environ;
+
+int
+putenv(const char *str)
+{
+	char *s1, *s2, **e;
+	int n;
+
+	for(n = 0; s2 = environ[n]; n++)
+		for(s1 = str; *s1 == *s2; s1++, s2++)
+			if(*s1 == '\0' || *s1 == '='){
+				environ[n] = str;
+				return 0;
+			}
+	e = realloc(environ, (n+1) * sizeof(char*));
+	if(e == 0)
+		return -1;
+	environ = e;
+	e[n++] = str;
+	e[n] = 0;
+	return 0;
+}