diff --git a/fortran/lammps.f90 b/fortran/lammps.f90
index d0133f075c..c297bad2ef 100644
--- a/fortran/lammps.f90
+++ b/fortran/lammps.f90
@@ -3687,7 +3687,7 @@ CONTAINS
 
     n = LEN_TRIM(f_string)
     ptr = lammps_malloc(n+1)
-    CALL C_F_POINTER(ptr, c_string, [1])
+    CALL C_F_POINTER(ptr, c_string, [n+1])
     DO i=1, n
         c_string(i) = f_string(i:i)
     END DO