diff --git a/src/frontend/arm/types.h b/src/frontend/arm/types.h
index 61562729..276409d3 100644
--- a/src/frontend/arm/types.h
+++ b/src/frontend/arm/types.h
@@ -39,13 +39,13 @@ enum class ExtReg {
     D24, D25, D26, D27, D28, D29, D30, D31,
 };
 
-using Imm3 = u32;
-using Imm4 = u32;
-using Imm5 = u32;
-using Imm7 = u32;
-using Imm8 = u32;
-using Imm11 = u32;
-using Imm12 = u32;
+using Imm3 = u8;
+using Imm4 = u8;
+using Imm5 = u8;
+using Imm7 = u8;
+using Imm8 = u8;
+using Imm11 = u16;
+using Imm12 = u16;
 using Imm24 = u32;
 using RegList = u16;