diff --git a/lib/hcl-prv.h b/lib/hcl-prv.h
index 7560a39..eeb0909 100644
--- a/lib/hcl-prv.h
+++ b/lib/hcl-prv.h
@@ -860,6 +860,7 @@ enum hcl_flx_state_t
 	HCL_FLX_DOLLARED_IDENT,
 	HCL_FLX_HMARKED_TOKEN,  /* hash-marked token */
 	HCL_FLX_HMARKED_B,      /* #b - intermediate state before #b[ or #b-radixed binary number */
+	HCL_FLX_HMARKED_BINOP,  /* #++ - binary operator symbol */
 	HCL_FLX_HMARKED_CHAR,   /* hash-marked character that begins with #\ */
 	HCL_FLX_HMARKED_IDENT,  /* hash-marked identifier like #include, etc */
 	HCL_FLX_HMARKED_NUMBER, /* hash-marked number - radixed number like #xABCD */
diff --git a/lib/read.c b/lib/read.c
index aab95b0..20754a8 100644
--- a/lib/read.c
+++ b/lib/read.c
@@ -272,6 +272,7 @@ static HCL_INLINE int is_delimchar (hcl_ooci_t c)
 	       c == '#' || c == '\"' || c == '\'' || c == '\\' || is_spacechar(c) || c == HCL_OOCI_EOF;
 }
 
+
 int hcl_is_binop_char (hcl_ooci_t c)
 {
 	return c == '&' || c == '*' || c == '+' || c == '-' || c == '/' || c == '%' ||
@@ -2458,6 +2459,13 @@ static int flx_hmarked_token (hcl_t* hcl, hcl_ooci_t c)
 	 * #"..."   symbol literal
 	 */
 
+	if (hcl_is_binop_char(c))
+	{
+		reset_flx_token (hcl);
+		FEED_CONTINUE_WITH_CHAR (hcl, c, HCL_FLX_HMARKED_BINOP);
+		goto consumed;
+	}
+
 	switch (c)
 	{
 		case '#':
@@ -2707,6 +2715,34 @@ not_consumed:
 	return 0;
 }
 
+static int flx_hmarked_binop (hcl_t* hcl, hcl_ooci_t c)
+{
+	if (hcl_is_binop_char(c))
+	{
+		ADD_TOKEN_CHAR(hcl, c);
+		goto consumed;
+	}
+	else if (is_delimchar(c))
+	{
+		FEED_WRAP_UP(hcl, HCL_TOK_SYMLIT);
+		goto not_consumed;
+	}
+	else
+	{
+		hcl_setsynerrbfmt (hcl, HCL_SYNERR_SYMLIT,
+			TOKEN_LOC(hcl), HCL_NULL /* no token name as incomplete */,
+			"invalid binary selector character '%jc' after #%.*js",
+			c, TOKEN_NAME_LEN(hcl), TOKEN_NAME_PTR(hcl));
+		return -1;
+	}
+
+consumed:
+	return 1;
+
+not_consumed:
+	return 0;
+}
+
 static int flx_hmarked_number (hcl_t* hcl, hcl_ooci_t c)
 {
 	hcl_flx_hn_t* rn = FLX_HN(hcl);
@@ -3230,6 +3266,7 @@ static int feed_char (hcl_t* hcl, hcl_ooci_t c)
 		case HCL_FLX_DOLLARED_IDENT:   return flx_dollared_ident(hcl, c);
 		case HCL_FLX_HMARKED_TOKEN:    return flx_hmarked_token(hcl, c);
 		case HCL_FLX_HMARKED_B:        return flx_hmarked_b(hcl, c);
+		case HCL_FLX_HMARKED_BINOP:    return flx_hmarked_binop(hcl, c);
 		case HCL_FLX_HMARKED_CHAR:     return flx_hmarked_char(hcl, c);
 		case HCL_FLX_HMARKED_IDENT:    return flx_hmarked_ident(hcl, c);
 		case HCL_FLX_HMARKED_NUMBER:   return flx_hmarked_number(hcl, c);
diff --git a/t/feed-5001.err b/t/feed-5001.err
index 418b469..535b831 100644
--- a/t/feed-5001.err
+++ b/t/feed-5001.err
@@ -83,3 +83,7 @@ defun :* fun1() { ##ERROR: syntax error - function name not symbol in defun
 ---
 
 (10 + 20 30) ##ERROR: syntax error - too many operands
+
+---
+
+#**a     ##ERROR: syntax error - invalid binary selector character 'a' after #**