diff --git a/src/structs.h b/src/structs.h
index 5b88260..e8f5db3 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -5026,3 +5026,7 @@ typedef struct {
     linenr_T	spv_capcol_lnum;    // line number for "cap_col"
 #endif
 } spellvars_T;
+
+// Return the length of a string literal
+#define STRLEN_LITERAL(s) (sizeof(s) - 1)
+
diff --git a/src/tag.c b/src/tag.c
index 893415f..2e7a74d 100644
--- a/src/tag.c
+++ b/src/tag.c
@@ -3344,7 +3344,7 @@ get_tagfname(
 	    if (tnp->tn_hf_idx > tag_fnames.ga_len || *p_hf == NUL)
 		return FAIL;
 	    ++tnp->tn_hf_idx;
-	    STRCPY(buf, p_hf);
+	    vim_strncpy(buf, p_hf, MAXPATHL - 1);
 	    STRCPY(gettail(buf), "tags");
 #ifdef BACKSLASH_IN_FILENAME
 	    slash_adjust(buf);
diff --git a/src/testdir/test_help.vim b/src/testdir/test_help.vim
index 6c8b3ab..bf15a42 100644
--- a/src/testdir/test_help.vim
+++ b/src/testdir/test_help.vim
@@ -205,5 +205,13 @@ func Test_help_using_visual_match()
   call v9.CheckScriptFailure(lines, 'E149:')
 endfunc
 
+" This caused a buffer overflow
+func Test_helpfile_overflow()
+  let _helpfile = &helpfile
+  let &helpfile = repeat('A', 5000)
+  help
+  helpclose
+  let &helpfile = _helpfile
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab