diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index dae6d51..1a677d1 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -1424,7 +1424,7 @@
 		}
 	    }
 	    else
-		EMSG_RET_NULL(_(e_nopresub));
+		EMSG_RET_NULL(_(e_no_previous_substitute_regular_expression));
 	    break;
 
       case Magic('1'):
@@ -2491,7 +2491,7 @@
     int		flags;
 
     if (expr == NULL)
-	IEMSG_RET_NULL(_(e_null));
+	IEMSG_RET_NULL(_(e_null_argument));
 
     init_class_tab();
 
@@ -3115,7 +3115,7 @@
 	break;
 
       default:			// Oh dear.  Called inappropriately.
-	iemsg(_(e_re_corr));
+	iemsg(_(e_corrupted_regexp_program));
 #ifdef DEBUG
 	printf("Called regrepeat with op code %d\n", OP(p));
 #endif
@@ -4309,7 +4309,7 @@
 	    break;
 
 	  default:
-	    iemsg(_(e_re_corr));
+	    iemsg(_(e_corrupted_regexp_program));
 #ifdef DEBUG
 	    printf("Illegal op code %d\n", op);
 #endif
@@ -4709,7 +4709,7 @@
 	{
 	    // We get here only if there's trouble -- normally "case END" is
 	    // the terminating point.
-	    iemsg(_(e_re_corr));
+	    iemsg(_(e_corrupted_regexp_program));
 #ifdef DEBUG
 	    printf("Premature EOL\n");
 #endif
@@ -4859,7 +4859,7 @@
     // Be paranoid...
     if (prog == NULL || line == NULL)
     {
-	iemsg(_(e_null));
+	iemsg(_(e_null_argument));
 	goto theend;
     }