diff --git a/tools/argdist.py b/tools/argdist.py
index 3bcf43a47740b6ce075fff2ee22b1663402d12ef..f6bb8bfed8d9ba4d6a025d1c47cffad66c505177 100755
--- a/tools/argdist.py
+++ b/tools/argdist.py
@@ -258,7 +258,7 @@ static inline bool %s(char const *ignored, char const *str) {
         char needle[] = %s;
         char haystack[sizeof(needle)];
         bpf_probe_read(&haystack, sizeof(haystack), (void *)str);
-        for (int i = 0; i < sizeof(needle); ++i) {
+        for (int i = 0; i < sizeof(needle)-1; ++i) {
                 if (needle[i] != haystack[i]) {
                         return false;
                 }