diff --git a/vvp/lexor.lex b/vvp/lexor.lex
index 0a266b389..fb2ec4ade 100644
--- a/vvp/lexor.lex
+++ b/vvp/lexor.lex
@@ -184,11 +184,11 @@
       return T_INSTR; }
 
 [0-9][0-9]* {
-      yylval.numb = strtol(yytext, 0, 0);
+      yylval.numb = strtoul(yytext, 0, 0);
       return T_NUMBER; }
 
 "0x"[0-9a-fA-F]+ {
-      yylval.numb = strtol(yytext, 0, 0);
+      yylval.numb = strtoul(yytext, 0, 0);
       return T_NUMBER; }
 
   /* Handle some specialized constant/literals as symbols. */
diff --git a/vvp/parse.y b/vvp/parse.y
index 729a0158d..fd12da226 100644
--- a/vvp/parse.y
+++ b/vvp/parse.y
@@ -47,7 +47,7 @@ static struct __vpiModPath*modpath_dst = 0;
 %union {
       char*text;
       char **table;
-      long numb;
+      unsigned long numb;
       bool flag;
 
       comp_operands_t opa;
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index b170cb01f..0f00ac35f 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -1102,7 +1102,7 @@ static bool of_CMPIU_the_hard_way(vthread_t thr, vvp_code_t cp)
 {
 
       unsigned idx1 = cp->bit_idx[0];
-      unsigned imm  = cp->bit_idx[1];
+      unsigned long imm  = cp->bit_idx[1];
       unsigned wid  = cp->number;
       if (idx1 >= 4)
 	    thr_check_addr(thr, idx1+wid-1);
@@ -1116,8 +1116,8 @@ static bool of_CMPIU_the_hard_way(vthread_t thr, vvp_code_t cp)
 
       vvp_bit4_t eq  = BIT4_0;
       for (unsigned idx = 0 ;  idx < wid ;  idx += 1) {
-	    vvp_bit4_t rv = (imm & 1)? BIT4_1 : BIT4_0;
-	    imm >>= 1;
+	    vvp_bit4_t rv = (imm & 1UL)? BIT4_1 : BIT4_0;
+	    imm >>= 1UL;
 
 	    if (bit4_is_xz(lv)) {
 		  eq = BIT4_X;