diff --git a/CHANGES b/CHANGES
index 366d527..18bb8e9 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+0.9:
+  fmt_str did not check for out==NULL!  Thanks, Uwe Ohse.
+
 0.8:
   BSD compatibility.
   fix mmap_shared.
diff --git a/fmt/fmt_str.c b/fmt/fmt_str.c
index 221c33c..0130f19 100644
--- a/fmt/fmt_str.c
+++ b/fmt/fmt_str.c
@@ -4,10 +4,10 @@ unsigned int fmt_str(char *out,const char *in) {
   register char* s=out;
   register const char* t=in;
   for (;;) {
-    if (!*t) break; *s=*t; ++s; ++t;
-    if (!*t) break; *s=*t; ++s; ++t;
-    if (!*t) break; *s=*t; ++s; ++t;
-    if (!*t) break; *s=*t; ++s; ++t;
+    if (!*t) break; if (s) { *s=*t; ++s; } ++t;
+    if (!*t) break; if (s) { *s=*t; ++s; } ++t;
+    if (!*t) break; if (s) { *s=*t; ++s; } ++t;
+    if (!*t) break; if (s) { *s=*t; ++s; } ++t;
   }
-  return s-out;
+  return t-in;
 }
diff --git a/t.c b/t.c
index a37bfb7..632a47a 100644
--- a/t.c
+++ b/t.c
@@ -14,7 +14,10 @@
      __asm__ __volatile__ ("rdtsc" : "=a" (low) : : "edx")
 
 int main(int argc,char* argv[]) {
-#if 1
+  char buf[100];
+  printf("%d\n",fmt_str(buf,"fnord"));
+  printf("%d\n",fmt_str(0,"fnord"));
+#if 0
   buffer_putulong(buffer_1,23);
 //  buffer_putspace(buffer_1);
   buffer_putsflush(buffer_1,"\n");