diff --git a/ivl_target.h b/ivl_target.h
index 959a6fb65..dc56b9a7f 100644
--- a/ivl_target.h
+++ b/ivl_target.h
@@ -201,7 +201,11 @@ typedef enum ivl_dis_domain_e {
       IVL_DIS_CONTINUOUS = 2
 } ivl_dis_domain_t;
 
+#if defined(__cplusplus) && !defined(__GNUC__)
+typedef enum ivl_drive_e : unsigned int {
+#else
 typedef enum ivl_drive_e {
+#endif
       IVL_DR_HiZ    = 0,
       IVL_DR_SMALL  = 1,
       IVL_DR_MEDIUM = 2,
@@ -243,7 +247,11 @@ typedef enum ivl_expr_type_e {
       IVL_EX_UNARY = 14
 } ivl_expr_type_t;
 
+#if defined(__cplusplus) && !defined(__GNUC__)
+typedef enum ivl_select_type_e : unsigned int {
+#else
 typedef enum ivl_select_type_e {
+#endif
       IVL_SEL_OTHER = 0,
       IVL_SEL_IDX_UP = 1,
       IVL_SEL_IDX_DOWN = 2
@@ -345,7 +353,11 @@ typedef enum ivl_path_edge_e {
 
 /* Processes are initial, always, or final blocks with a statement. This is
    the type of the ivl_process_t object. */
+#if defined(__cplusplus) && !defined(__GNUC__)
+typedef enum ivl_process_type_e : unsigned int {
+#else
 typedef enum ivl_process_type_e {
+#endif
       IVL_PR_INITIAL = 0,
       IVL_PR_ALWAYS  = 1,
       IVL_PR_FINAL   = 2
@@ -431,7 +443,11 @@ typedef enum ivl_sfunc_as_task_e {
 
 /* This is the type of a variable, and also used as the type for an
    expression. */
+#if defined(__cplusplus) && !defined(__GNUC__)
+typedef enum ivl_variable_type_e : unsigned int {
+#else
 typedef enum ivl_variable_type_e {
+#endif
       IVL_VT_VOID    = 0,  /* Not used */
       IVL_VT_NO_TYPE = 1,  /* Place holder for missing/unknown type. */
       IVL_VT_REAL    = 2,