diff --git a/incl/iss/arch/tgc_c.h b/incl/iss/arch/tgc_c.h
index 74ab760..619034d 100644
--- a/incl/iss/arch/tgc_c.h
+++ b/incl/iss/arch/tgc_c.h
@@ -53,7 +53,7 @@ template <> struct traits<tgc_c> {
     static constexpr std::array<const char*, 36> reg_aliases{
         {"ZERO", "RA", "SP", "GP", "TP", "T0", "T1", "T2", "S0", "S1", "A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7", "S2", "S3", "S4", "S5", "S6", "S7", "S8", "S9", "S10", "S11", "T3", "T4", "T5", "T6", "PC", "NEXT_PC", "PRIV", "DPC"}};
 
-    enum constants {MISA_VAL=0b01000000000000000001000100000100, MARCHID_VAL=0x80000003, RFS=32, XLEN=32, CSR_SIZE=4096, INSTR_ALIGNMENT=2, fence=0, fencei=1, fencevmal=2, fencevmau=3, MUL_LEN=64};
+    enum constants {MISA_VAL=0b01000000000000000001000100000100, MARCHID_VAL=0x80000003, RFS=32, INSTR_ALIGNMENT=2, XLEN=32, CSR_SIZE=4096, fence=0, fencei=1, fencevmal=2, fencevmau=3, MUL_LEN=64};
 
     constexpr static unsigned FP_REGS_SIZE = 0;
 
diff --git a/src/vm/interp/vm_tgc_c.cpp b/src/vm/interp/vm_tgc_c.cpp
index 52fd588..ea76eaf 100644
--- a/src/vm/interp/vm_tgc_c.cpp
+++ b/src/vm/interp/vm_tgc_c.cpp
@@ -2001,7 +2001,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rs1_idx = rs1 + 8;
+		            uint8_t rs1_idx = rs1 + 8;
 		            *(X+rs1_idx) = *(X+rs1_idx) >> shamt;
 		        }
 		        } catch(...){}
@@ -2024,11 +2024,11 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        if(shamt) {
-		            uint32_t rs1_idx = rs1 + 8;
+		            uint8_t rs1_idx = rs1 + 8;
 		            *(X+rs1_idx) = ((int32_t)*(X+rs1_idx)) >> shamt;
 		        }
 		        else if(traits::XLEN == 128) {
-		            uint32_t rs1_idx = rs1 + 8;
+		            uint8_t rs1_idx = rs1 + 8;
 		            *(X+rs1_idx) = ((int32_t)*(X+rs1_idx)) >>  64;
 		        }
 		        } catch(...){}
@@ -2051,7 +2051,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rs1_idx = rs1 +  8;
+		            uint8_t rs1_idx = rs1 +  8;
 		            *(X+rs1_idx) = *(X+rs1_idx) & (int8_t)sext<6>(imm);
 		        }
 		        } catch(...){}
@@ -2074,7 +2074,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rd_idx = rd +  8;
+		            uint8_t rd_idx = rd +  8;
 		            *(X+rd_idx) = *(X+rd_idx) - *(X+rs2 +  8);
 		        }
 		        } catch(...){}
@@ -2097,7 +2097,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rd_idx = rd +  8;
+		            uint8_t rd_idx = rd +  8;
 		            *(X+rd_idx) = *(X+rd_idx) ^ *(X+rs2 +  8);
 		        }
 		        } catch(...){}
@@ -2120,7 +2120,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rd_idx = rd +  8;
+		            uint8_t rd_idx = rd +  8;
 		            *(X+rd_idx) = *(X+rd_idx) | *(X+rs2 +  8);
 		        }
 		        } catch(...){}
@@ -2143,7 +2143,7 @@ typename vm_base<ARCH>::virt_addr_t vm_impl<ARCH>::execute_inst(finish_cond_e co
 		        // execute instruction
 		        try {
 		        {
-		            uint32_t rd_idx = rd +  8;
+		            uint8_t rd_idx = rd +  8;
 		            *(X+rd_idx) = *(X+rd_idx) & *(X+rs2 +  8);
 		        }
 		        } catch(...){}