--- a/msktconf.cpp
+++ b/msktconf.cpp
@@ -162,7 +162,7 @@
         switch_default_ccache(ccache_name);
         return true;
     } catch (KRB5Exception &e) {
-        VERBOSE(e.what());
+        VERBOSE("%s", e.what());
         if (e.err() == KRB5KDC_ERR_KEY_EXP) {
             VERBOSE("Password needs to be changed");
             flags->password_expired = true;
@@ -186,7 +186,7 @@
 	switch_default_ccache(ccache_name.c_str());
         return true;
     } catch (KRB5Exception &e) {
-        VERBOSE(e.what());
+        VERBOSE("%s", e.what());
         VERBOSE("Authentication with password failed");
         return false;
     }
