diff --git a/spot/twa/acc.cc b/spot/twa/acc.cc
index 4c4013ce7..0549ce462 100644
--- a/spot/twa/acc.cc
+++ b/spot/twa/acc.cc
@@ -2134,7 +2134,7 @@ namespace spot
       if (*input != c)
         {
           char msg[20];
-          sprintf(msg, "was expecting %c '.'", c);
+          std::snprintf(msg, sizeof msg, "was expecting '%c'.", c);
           syntax_error(input, msg);
         }
       ++input;
diff --git a/spot/twaalgos/aiger.cc b/spot/twaalgos/aiger.cc
index 6b608dd59..7d724b124 100644
--- a/spot/twaalgos/aiger.cc
+++ b/spot/twaalgos/aiger.cc
@@ -2224,7 +2224,7 @@ namespace spot
     // vars are unsigned -> 10 digits at most
     char gate_buffer[3 * 10 + 5];
     auto write_gate = [&](unsigned o, unsigned i0, unsigned i1) {
-      std::sprintf(gate_buffer, "%u %u %u\n", o, i0, i1);
+      std::snprintf(gate_buffer, sizeof gate_buffer, "%u %u %u\n", o, i0, i1);
       os << gate_buffer;
     };
     // Count active gates