diff --git a/src/simd_128.h b/src/simd_128.h
index db23be43..5826bb65 100644
--- a/src/simd_128.h
+++ b/src/simd_128.h
@@ -40,19 +40,19 @@ typedef __m128i VecType;
 
 /* ============= Constant variable  ============ */
 
-#define F4_U32 _mm_set1_epi32(65537)
-#define F4_MINUS_ONE_U32 _mm_set1_epi32(65536)
-#define F3_U32 _mm_set1_epi32(257)
-#define F3_MINUS_ONE_U32 _mm_set1_epi32(256)
+const VecType F4_U32 = _mm_set1_epi32(65537);
+const VecType F4_MINUS_ONE_U32 = _mm_set1_epi32(65536);
+const VecType F3_U32 = _mm_set1_epi32(257);
+const VecType F3_MINUS_ONE_U32 = _mm_set1_epi32(256);
 
-#define F3_U16 _mm_set1_epi16(257)
-#define F3_MINUS_ONE_U16 _mm_set1_epi16(256)
+const VecType F3_U16 = _mm_set1_epi16(257);
+const VecType F3_MINUS_ONE_U16 = _mm_set1_epi16(256);
 
-#define ZERO (_mm_setzero_si128())
-#define ONE_U16 (_mm_set1_epi16(1))
-#define ONE_U32 (_mm_set1_epi32(1))
+const VecType ZERO = _mm_setzero_si128();
+const VecType ONE_U16 = _mm_set1_epi16(1);
+const VecType ONE_U32 = _mm_set1_epi32(1);
 
-#define MASK8_LO (_mm_set1_epi16(0x80))
+const VecType MASK8_LO = _mm_set1_epi16(0x80);
 
 /* ============= Essential Operations for SSE w/ both u16 & u32 ============ */
 
diff --git a/src/simd_256.h b/src/simd_256.h
index 4539fc34..e8304b78 100644
--- a/src/simd_256.h
+++ b/src/simd_256.h
@@ -53,19 +53,19 @@ typedef __m128i HalfVecType;
 
 /* ============= Constant variable  ============ */
 
-#define F4_U32 _mm256_set1_epi32(65537)
-#define F4_MINUS_ONE_U32 _mm256_set1_epi32(65536)
-#define F3_U32 _mm256_set1_epi32(257)
-#define F3_MINUS_ONE_U32 _mm256_set1_epi32(256)
+const VecType F4_U32 = _mm256_set1_epi32(65537);
+const VecType F4_MINUS_ONE_U32 = _mm256_set1_epi32(65536);
+const VecType F3_U32 = _mm256_set1_epi32(257);
+const VecType F3_MINUS_ONE_U32 = _mm256_set1_epi32(256);
 
-#define F3_U16 _mm256_set1_epi16(257)
-#define F3_MINUS_ONE_U16 _mm256_set1_epi16(256)
+const VecType F3_U16 = _mm256_set1_epi16(257);
+const VecType F3_MINUS_ONE_U16 = _mm256_set1_epi16(256);
 
-#define ZERO (_mm256_setzero_si256())
-#define ONE_U16 (_mm256_set1_epi16(1))
-#define ONE_U32 (_mm256_set1_epi32(1))
+const VecType ZERO = _mm256_setzero_si256();
+const VecType ONE_U16 = _mm256_set1_epi16(1);
+const VecType ONE_U32 = _mm256_set1_epi32(1);
 
-#define MASK8_LO (_mm256_set1_epi16(0x80))
+const VecType MASK8_LO = _mm256_set1_epi16(0x80);
 
 /* ============= Essential Operations for AVX2 w/ both u16 & u32 ============ */