diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 18bad80..698ff04 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -1503,6 +1503,14 @@
 		    break;
 
 		case '#':
+		    if (regparse[0] == '=' && regparse[1] >= 48
+							  && regparse[1] <= 50)
+		    {
+			// misplaced \%#=1
+			semsg(_(e_atom_engine_must_be_at_start_of_pattern),
+								  regparse[1]);
+			return FAIL;
+		    }
 		    ret = regnode(CURSOR);
 		    break;