diff --git a/src/library.cpp b/src/library.cpp
index 54497970ad..6f283ea4da 100644
--- a/src/library.cpp
+++ b/src/library.cpp
@@ -1620,16 +1620,16 @@ void lammps_set_fix_external_callback(void *ptr, char *id, FixExternalFnPtr call
   {
     int ifix = lmp->modify->find_fix(id);
     if (ifix < 0) {
-      char str[50];
-      snprintf(str, 50, "Can not find fix with ID '%s'!", id);
+      char str[128];
+      snprintf(str, 128, "Can not find fix with ID '%s'!", id);
       lmp->error->all(FLERR,str);
     }
 
     Fix *fix = lmp->modify->fix[ifix];
 
     if (strcmp("external",fix->style) != 0){
-      char str[50];
-      snprintf(str, 50, "Fix '%s' is not of style external!", id);
+      char str[128];
+      snprintf(str, 128, "Fix '%s' is not of style external!", id);
       lmp->error->all(FLERR,str);
     }