diff --git a/src/ex_getln.c b/src/ex_getln.c
index 471479c..7ef304d 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -5095,6 +5095,26 @@
 	ret = expand_wildcards_eval(&pat, num_file, file, flags);
 	if (free_pat)
 	    vim_free(pat);
+#ifdef BACKSLASH_IN_FILENAME
+	if (p_csl[0] != NUL)
+	{
+	    int	    i;
+
+	    for (i = 0; i < *num_file; ++i)
+	    {
+		char_u	*ptr = (*file)[i];
+
+		while (*ptr != NUL)
+		{
+		    if (p_csl[0] == 's' && *ptr == '\\')
+			*ptr = '/';
+		    else if (p_csl[0] == 'b' && *ptr == '/')
+			*ptr = '\\';
+		    ptr += (*mb_ptr2len)(ptr);
+		}
+	    }
+	}
+#endif
 	return ret;
     }
 
diff --git a/src/insexpand.c b/src/insexpand.c
index fe475a5..4245800 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -2669,6 +2669,26 @@
 
 		// May change home directory back to "~".
 		tilde_replace(compl_pattern, num_matches, matches);
+#ifdef BACKSLASH_IN_FILENAME
+		if (curbuf->b_p_csl[0] != NUL)
+		{
+		    int	    i;
+
+		    for (i = 0; i < num_matches; ++i)
+		    {
+			char_u	*ptr = matches[i];
+
+			while (*ptr != NUL)
+			{
+			    if (curbuf->b_p_csl[0] == 's' && *ptr == '\\')
+				*ptr = '/';
+			    else if (curbuf->b_p_csl[0] == 'b' && *ptr == '/')
+				*ptr = '\\';
+			    ptr += (*mb_ptr2len)(ptr);
+			}
+		    }
+		}
+#endif
 		ins_compl_add_matches(num_matches, matches, p_fic || p_wic);
 	    }
 	    break;
diff --git a/src/option.c b/src/option.c
index 3959d47..fdad205 100644
--- a/src/option.c
+++ b/src/option.c
@@ -88,6 +88,7 @@
 # define PV_DICT	OPT_BOTH(OPT_BUF(BV_DICT))
 # define PV_TSR		OPT_BOTH(OPT_BUF(BV_TSR))
 #endif
+#define PV_CSL		OPT_BUF(BV_CSL)
 #ifdef FEAT_COMPL_FUNC
 # define PV_CFU		OPT_BUF(BV_CFU)
 #endif
@@ -892,6 +893,15 @@
 			    {(char_u *)0L, (char_u *)0L}
 #endif
 			    SCTX_INIT},
+    {"completeslash",   "csl",  P_STRING|P_VI_DEF|P_VIM,
+#if defined(FEAT_INS_EXPAND) && defined(BACKSLASH_IN_FILENAME)
+			    (char_u *)&p_csl, PV_CSL,
+			    {(char_u *)"", (char_u *)0L}
+#else
+			    (char_u *)NULL, PV_NONE,
+			    {(char_u *)0L, (char_u *)0L}
+#endif
+			    SCTX_INIT},
     {"confirm",     "cf",   P_BOOL|P_VI_DEF,
 #if defined(FEAT_GUI_DIALOG) || defined(FEAT_CON_DIALOG)
 			    (char_u *)&p_confirm, PV_NONE,
@@ -3238,6 +3248,9 @@
 #endif
 #ifdef FEAT_INS_EXPAND
 static char *(p_cot_values[]) = {"menu", "menuone", "longest", "preview", "noinsert", "noselect", NULL};
+# ifdef BACKSLASH_IN_FILENAME
+static char *(p_csl_values[]) = {"slash", "backslash", NULL};
+# endif
 #endif
 #ifdef FEAT_SIGNS
 static char *(p_scl_values[]) = {"yes", "no", "auto", "number", NULL};
@@ -7409,7 +7422,7 @@
 	}
     }
 
-    /* 'completeopt' */
+    // 'completeopt'
     else if (varp == &p_cot)
     {
 	if (check_opt_strings(p_cot, p_cot_values, TRUE) != OK)
@@ -7417,7 +7430,16 @@
 	else
 	    completeopt_was_set();
     }
-#endif /* FEAT_INS_EXPAND */
+
+# ifdef BACKSLASH_IN_FILENAME
+    // 'completeslash'
+    else if (varp == &curbuf->b_p_csl)
+    {
+	if (check_opt_strings(p_csl, p_csl_values, FALSE) != OK)
+	    errmsg = e_invarg;
+    }
+# endif
+#endif // FEAT_INS_EXPAND
 
 #ifdef FEAT_SIGNS
     // 'signcolumn'
@@ -11110,7 +11132,6 @@
 #endif
 	case PV_MENC:	return *curbuf->b_p_menc != NUL
 				    ? (char_u *)&(curbuf->b_p_menc) : p->var;
-
 #ifdef FEAT_ARABIC
 	case PV_ARAB:	return (char_u *)&(curwin->w_p_arab);
 #endif
@@ -11197,6 +11218,9 @@
 #endif
 #ifdef FEAT_INS_EXPAND
 	case PV_CPT:	return (char_u *)&(curbuf->b_p_cpt);
+# ifdef BACKSLASH_IN_FILENAME
+	case PV_CSL:	return (char_u *)&(curbuf->b_p_csl);
+# endif
 #endif
 #ifdef FEAT_COMPL_FUNC
 	case PV_CFU:	return (char_u *)&(curbuf->b_p_cfu);
@@ -11591,6 +11615,9 @@
 	    buf->b_p_swf = cmdmod.noswapfile ? FALSE : p_swf;
 #ifdef FEAT_INS_EXPAND
 	    buf->b_p_cpt = vim_strsave(p_cpt);
+# ifdef BACKSLASH_IN_FILENAME
+	    buf->b_p_csl = vim_strsave(p_csl);
+# endif
 #endif
 #ifdef FEAT_COMPL_FUNC
 	    buf->b_p_cfu = vim_strsave(p_cfu);
diff --git a/src/option.h b/src/option.h
index 0654667..29ecd8a 100644
--- a/src/option.h
+++ b/src/option.h
@@ -412,6 +412,9 @@
 EXTERN int	p_cp;		// 'compatible'
 #ifdef FEAT_INS_EXPAND
 EXTERN char_u	*p_cot;		// 'completeopt'
+# ifdef BACKSLASH_IN_FILENAME
+EXTERN char_u	*p_csl;		// 'completeslash'
+# endif
 EXTERN long	p_ph;		// 'pumheight'
 EXTERN long	p_pw;		// 'pumwidth'
 #endif
@@ -997,6 +1000,9 @@
     , BV_DICT
     , BV_TSR
 #endif
+#ifdef BACKSLASH_IN_FILENAME
+    , BV_CSL
+#endif
 #ifdef FEAT_COMPL_FUNC
     , BV_CFU
 #endif
diff --git a/src/structs.h b/src/structs.h
index 5841176..122e475 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1198,6 +1198,7 @@
 
 // Initial size for a hashtable.  Our items are relatively small and growing
 // is expensive, thus use 16 as a start.  Must be a power of 2.
+// This allows for storing 10 items (2/3 of 16) before a resize is needed.
 #define HT_INIT_SIZE 16
 
 typedef struct hashtable_S
@@ -2395,6 +2396,9 @@
 #ifdef FEAT_INS_EXPAND
     char_u	*b_p_cpt;	// 'complete'
 #endif
+#ifdef BACKSLASH_IN_FILENAME
+    char_u	*b_p_csl;	// 'completeslash'
+#endif
 #ifdef FEAT_COMPL_FUNC
     char_u	*b_p_cfu;	// 'completefunc'
     char_u	*b_p_ofu;	// 'omnifunc'
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index c028df3..29f4050 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -331,3 +331,50 @@
   delcom GetInput
   set wildmenu& wildchar&
 endfunc
+
+" Test for insert path completion with completeslash option
+func Test_ins_completeslash()
+  if !has('win32')
+    return
+  endif
+  
+  call mkdir('Xdir')
+
+  let orig_shellslash = &shellslash
+  set cpt&
+
+  new
+  
+  set noshellslash
+
+  set completeslash=
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir\', getline('.'))
+
+  set completeslash=backslash
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir\', getline('.'))
+
+  set completeslash=slash
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir/', getline('.'))
+
+  set shellslash
+
+  set completeslash=
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir/', getline('.'))
+
+  set completeslash=backslash
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir\', getline('.'))
+
+  set completeslash=slash
+  exe "normal oXd\<C-X>\<C-F>"
+  call assert_equal('Xdir/', getline('.'))
+  %bw!
+  call delete('Xdir', 'rf')
+
+  let &shellslash = orig_shellslash
+endfunc
+
diff --git a/src/version.c b/src/version.c
index 166b17c..2db2ee1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1769,
+/**/
     1768,
 /**/
     1767,