diff --git a/src/charset.c b/src/charset.c
index 3eb5b58..cff62e1 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1776,25 +1776,30 @@
  * If "what" contains STR2NR_HEX recognize hex numbers
  * If "what" contains STR2NR_FORCE always assume bin/oct/hex.
  * If maxlen > 0, check at a maximum maxlen chars.
+ * If strict is TRUE, check the number strictly. return *len = 0 if fail.
  */
     void
 vim_str2nr(
     char_u		*start,
-    int			*prep,	    /* return: type of number 0 = decimal, 'x'
-				       or 'X' is hex, '0' = octal, 'b' or 'B'
-				       is bin */
-    int			*len,	    /* return: detected length of number */
-    int			what,	    /* what numbers to recognize */
-    varnumber_T		*nptr,	    /* return: signed result */
-    uvarnumber_T	*unptr,	    /* return: unsigned result */
-    int			maxlen)     /* max length of string to check */
+    int			*prep,	    // return: type of number 0 = decimal, 'x'
+				    // or 'X' is hex, '0' = octal, 'b' or 'B'
+				    // is bin
+    int			*len,	    // return: detected length of number
+    int			what,	    // what numbers to recognize
+    varnumber_T		*nptr,	    // return: signed result
+    uvarnumber_T	*unptr,	    // return: unsigned result
+    int			maxlen,     // max length of string to check
+    int			strict)     // check strictly
 {
     char_u	    *ptr = start;
-    int		    pre = 0;		/* default is decimal */
+    int		    pre = 0;		// default is decimal
     int		    negative = FALSE;
     uvarnumber_T    un = 0;
     int		    n;
 
+    if (len != NULL)
+	*len = 0;
+
     if (ptr[0] == '-')
     {
 	negative = TRUE;
@@ -1836,9 +1841,7 @@
 	}
     }
 
-    /*
-    * Do the string-to-numeric conversion "manually" to avoid sscanf quirks.
-    */
+    // Do the conversion manually to avoid sscanf() quirks.
     n = 1;
     if (pre == 'B' || pre == 'b' || what == STR2NR_BIN + STR2NR_FORCE)
     {
@@ -1907,6 +1910,10 @@
 		break;
 	}
     }
+    // Check for an alpha-numeric character immediately following, that is
+    // most likely a typo.
+    if (strict && n - 1 != maxlen && ASCII_ISALNUM(*ptr))
+	return;
 
     if (prep != NULL)
 	*prep = pre;