diff --git a/src/frontend/logicexp.c b/src/frontend/logicexp.c
index 3d3df6ea9..46b061ac8 100644
--- a/src/frontend/logicexp.c
+++ b/src/frontend/logicexp.c
@@ -569,11 +569,22 @@ static void move_inputs(struct gate_data *curr, struct gate_data *prev)
     prev->finished = TRUE;
 }
 
-static void scan_gates(DSTRING *lhs)
+static void scan_gates(DSTRING *lhs, int optimize)
 {
     struct gate_data *current = NULL, *previous = NULL, *last_curr = NULL;
     struct gate_data *prev = NULL;
 
+    if (optimize < 1) {
+        current = last_gate;
+        if (ds_get_length(lhs) > 0) {
+            assert(current->finished == FALSE);
+            tfree(current->outp);
+            current->outp = TMALLOC(char, ds_get_length(lhs) + 1);
+            strcpy(current->outp, ds_get_buf(lhs));
+        }
+        return;
+    }
+
     current = first_gate;
     while (current) {
         int is_gate = (current->type == '&'
@@ -581,7 +592,8 @@ static void scan_gates(DSTRING *lhs)
                        || current->type == '|');
         previous = current->prev;
         if (is_gate && current->is_possible) {
-            if (previous && previous->type == current->type) {
+            if (previous && previous->type == current->type
+            && previous->is_not == current->is_not) {
                 if (eq(current->ins->name, previous->outp)) {
                     move_inputs(current, previous);
                 }
@@ -608,6 +620,7 @@ static void scan_gates(DSTRING *lhs)
                 prev = current->prev;
                 while (prev) {
                     if (prev->type == current->type
+                    && prev->is_not == current->is_not
                     && prev->finished == FALSE
                     && strncmp(prev->outp, TMP_PREFIX, TMP_LEN) == 0
                     && eq(current->ins->name, prev->outp)) {
@@ -748,36 +761,44 @@ static int infix_to_postfix(char* infix, DSTRING * postfix_p)
     nlist = add_name_entry("first", NULL);
     ds_clear(postfix_p);
     while ( ( ltok = lexer_scan(lx) ) != 0 ) { // start while ltok loop
-        if (ltok == LEX_ID && last_tok == LEX_ID) {
-            fprintf(stderr, "ERROR (1) no gate operator between two identifiers\n");
-            status = 1;
-            goto err_return;
-        }
-        if (lex_gate_op(ltok)) {
-            if (lex_gate_op(last_tok)) {
-                fprintf(stderr, "ERROR (2) two consecutive gate operators\n");
-                status = 1;
-                goto err_return;
-            } else if (last_tok != LEX_ID && last_tok != ')') {
-                fprintf(stderr, "ERROR (2a) gate operator not after ID or rparen\n");
+        if (last_tok == -1) { // check starting token
+            if (!(ltok == LEX_ID || ltok == '~' || ltok == '(')) {
+                fprintf(stderr, "ERROR (1) invalid starting token\n");
                 status = 1;
                 goto err_return;
             }
-        }
-        if (last_tok == '~' && ltok != LEX_ID && ltok != '(') {
-            fprintf(stderr, "ERROR (3) \'~\' is not followed by an ID or lparen\n");
-            status = 1;
-            goto err_return;
-        }
-        if (ltok == '~' && (last_tok == LEX_ID || last_tok == ')')) {
-            fprintf(stderr, "ERROR (4) \'~\' follows an ID or rparen\n");
-            status = 1;
-            goto err_return;
-        }
-        if (ltok == ')' && (lex_gate_op(last_tok) || last_tok == '~')) {
-            fprintf(stderr, "ERROR (5) incomplete infix sub-expression\n");
-            status = 1;
-            goto err_return;
+        } else {
+            if (last_tok == LEX_ID) { // check follower of an ID
+                if (!(lex_gate_op(ltok) || ltok == ')')) {
+                    fprintf(stderr, "ERROR (2) incorrect token after ID\n");
+                    status = 1;
+                    goto err_return;
+                }
+            } else if (lex_gate_op(last_tok)) { // check follower of a gate op
+                if (!(ltok == LEX_ID || ltok == '~' || ltok == '(')) {
+                    fprintf(stderr, "ERROR (3) incorrect token after gate op\n");
+                    status = 1;
+                    goto err_return;
+                }
+            } else if (last_tok == '~') { // check follower of ~
+                if (!(ltok == LEX_ID || ltok == '(')) {
+                    fprintf(stderr, "ERROR (4) incorrect token after \'~\'\n");
+                    status = 1;
+                    goto err_return;
+                }
+            } else if (last_tok == '(') { // check follower of lparen
+                if (!(ltok == LEX_ID || ltok == '~' || ltok == '(')) {
+                    fprintf(stderr, "ERROR (5) incorrect token after lparen\n");
+                    status = 1;
+                    goto err_return;
+                }
+            } else if (last_tok == ')') { // check follower of rparen
+                if (!(ltok == ')' || lex_gate_op(ltok))) {
+                    fprintf(stderr, "ERROR (6) incorrect token after rparen\n");
+                    status = 1;
+                    goto err_return;
+                }
+            }
         }
 
         last_tok = ltok;
@@ -797,6 +818,11 @@ static int infix_to_postfix(char* infix, DSTRING * postfix_p)
             }
         } else if (ltok == ')') {
             rparen_count++;
+            if (rparen_count > lparen_count) {
+                fprintf(stderr, "ERROR (9a) mismatched rparen\n");
+                status = 1;
+                goto err_return;
+            }
             while ( stack.top != -1 && !eq(stack.array[stack.top], "(") ) {
                 ds_cat_printf(postfix_p, " %s", pop(&stack, &status));
                 if (status) {
@@ -832,19 +858,19 @@ static int infix_to_postfix(char* infix, DSTRING * postfix_p)
                 goto err_return;
             }
         } else {
-            fprintf(stderr, "ERROR (6) unexpected infix token %d \'%s\'\n",
+            fprintf(stderr, "ERROR (7) unexpected infix token %d \'%s\'\n",
                 ltok, lx->lexer_buf);
             status = 1;
             goto err_return;
         }
     } // end while ltok loop
     if (lex_gate_op(last_tok) || last_tok == '~') {
-        fprintf(stderr, "ERROR (7) incomplete infix expression\n");
+        fprintf(stderr, "ERROR (8) incomplete infix expression\n");
         status = 1;
         goto err_return;
     }
     if (lparen_count != rparen_count) {
-        fprintf(stderr, "ERROR (8) mismatched parentheses\n");
+        fprintf(stderr, "ERROR (9) mismatched parentheses\n");
         status = 1;
         goto err_return;
     }
@@ -966,7 +992,7 @@ err_return:
 /* Start of logicexp parser */
 static void aerror(char *s);
 static BOOL amatch(int t);
-static BOOL bparse(char *line, BOOL new_lexer);
+static BOOL bparse(char *line, BOOL new_lexer, int optimize);
 
 static int lookahead = 0;
 static int number_of_instances = 0;
@@ -1061,7 +1087,7 @@ static BOOL amatch(int t)
     return TRUE;
 }
 
-static BOOL bstmt_postfix(void)
+static BOOL bstmt_postfix(int optimize)
 {
     /* A stmt is: output_name_id = '{' expr '}' */
     DS_CREATE(lhs, 32);
@@ -1113,7 +1139,7 @@ static BOOL bstmt_postfix(void)
         retval = FALSE;
         goto bail_out;
     }
-    scan_gates(&lhs);
+    scan_gates(&lhs, optimize);
     gen_scanned_gates(first_gate);
     lookahead = lex_scan();
     while (lookahead != '}') {
@@ -1156,7 +1182,7 @@ static char *get_logicexp_tmodel_delays(
     return ds_get_buf(mname);
 }
 
-static BOOL bparse(char *line, BOOL new_lexer)
+static BOOL bparse(char *line, BOOL new_lexer, int optimize)
 {
     BOOL ret_val = TRUE;
     DS_CREATE(stmt, LEX_BUF_SZ);
@@ -1171,7 +1197,7 @@ static BOOL bparse(char *line, BOOL new_lexer)
     while (lookahead != '\0') {
         ds_clear(&stmt);
         ds_cat_str(&stmt, parse_lexer->lexer_buf);
-        if (!bstmt_postfix()) {
+        if (!bstmt_postfix(optimize)) {
             cleanup_parser();
             ret_val= FALSE;
             break;
@@ -1233,8 +1259,9 @@ static BOOL expect_token(
     return TRUE;
 }
 
-BOOL f_logicexp(char *line)
+BOOL f_logicexp(char *line, int optimize)
 {
+    /* If optimize > 0 then perform optimizations in scan_gates */
     int t, num_ins = 0, num_outs = 0, i;
     char *endp;
     BOOL ret_val = TRUE;
@@ -1319,7 +1346,7 @@ BOOL f_logicexp(char *line)
     }
     (void) add_sym_tab_entry(parse_lexer->lexer_buf,
         SYM_TMODEL, &parse_lexer->lexer_sym_tab);
-    ret_val = bparse(line, FALSE);
+    ret_val = bparse(line, FALSE, optimize);
 
     current_lexer = NULL;
     if (!ret_val) {
diff --git a/src/frontend/udevices.c b/src/frontend/udevices.c
index dcbe5d054..b7437f45e 100644
--- a/src/frontend/udevices.c
+++ b/src/frontend/udevices.c
@@ -280,6 +280,7 @@ static int ps_udevice_msgs = 0;  // Controls the verbosity of U* warnings
   If ps_udevice_exit is non-zero then exit when u_process_instance fails
 */
 static int ps_udevice_exit = 0;
+static int ps_scan_gates_optimize = 1;  // Allow optimization in scan_gates
 static int ps_tpz_delays = 0;  // For tristate delays
 static int ps_with_inverters = 0;  // For ff/latch control inputs
 static int ps_with_tri_inverters = 0;  // For inv3/inv3a data inputs
@@ -965,6 +966,9 @@ void initialize_udevice(char *subckt_line)
     if (!cp_getvar("ps_udevice_exit", CP_NUM, &ps_udevice_exit, 0)) {
         ps_udevice_exit = 0;
     }
+    if (!cp_getvar("ps_scan_gates_optimize", CP_NUM, &ps_scan_gates_optimize, 0)) {
+        ps_scan_gates_optimize = 1;
+    }
     /* If non-zero use inverters with ff/latch control inputs */
     if (!cp_getvar("ps_with_inverters", CP_NUM, &ps_with_inverters, 0)) {
         ps_with_inverters = 0;
@@ -4318,7 +4322,7 @@ BOOL u_process_instance(char *nline)
             if (ps_ports_and_pins & 4) {
                 printf("TRANS_IN  %s\n", nline);
             }
-            behav_ret = f_logicexp(nline);
+            behav_ret = f_logicexp(nline, ps_scan_gates_optimize);
             if (!behav_ret && current_subckt) {
                 fprintf(stderr, "ERROR in %s\n", current_subckt);
             }
diff --git a/src/include/ngspice/logicexp.h b/src/include/ngspice/logicexp.h
index 556835a43..8c77e9a09 100644
--- a/src/include/ngspice/logicexp.h
+++ b/src/include/ngspice/logicexp.h
@@ -3,7 +3,7 @@
 #ifndef INCLUDED_LOGICEXP_H
 #define INCLUDED_LOGICEXP_H
 
-BOOL f_logicexp(char *line);
+BOOL f_logicexp(char *line, int optimize);
 BOOL f_pindly(char *line);
 
 #endif