diff --git a/README.md b/README.md
index eb4e1e3..b79e44a 100644
--- a/README.md
+++ b/README.md
@@ -56,7 +56,7 @@ data types.
 
 ## Arg sort routines on arrays
 ```cpp
-std::vector<size_t> arg = x86simdsort::argsort(T* arr, size_t size, bool hasnan, bool descending);
+std::vector<size_t> arg = x86simdsort::argsort(const T* arr, size_t size, bool hasnan, bool descending);
 std::vector<size_t> arg = x86simdsort::argselect(T* arr, size_t k, size_t size, bool hasnan);
 ```
 Supported datatypes: `T` $\in$ `[_Float16, uint16_t, int16_t, float, uint32_t, int32_t, double,
diff --git a/lib/x86simdsort-avx2.cpp b/lib/x86simdsort-avx2.cpp
index 58305dc..1e0761e 100644
--- a/lib/x86simdsort-avx2.cpp
+++ b/lib/x86simdsort-avx2.cpp
@@ -23,7 +23,7 @@
     } \
     template <> \
     std::vector<size_t> argsort( \
-            type *arr, size_t arrsize, bool hasnan, bool descending) \
+            const type *arr, size_t arrsize, bool hasnan, bool descending) \
     { \
         return x86simdsortStatic::argsort(arr, arrsize, hasnan, descending); \
     } \
diff --git a/lib/x86simdsort-internal.h b/lib/x86simdsort-internal.h
index a9ded64..f8a14c0 100644
--- a/lib/x86simdsort-internal.h
+++ b/lib/x86simdsort-internal.h
@@ -44,7 +44,7 @@
                                                bool hasnan = false, \
                                                bool descending = false); \
     template <typename T> \
-    XSS_HIDE_SYMBOL std::vector<size_t> argsort(T *arr, \
+    XSS_HIDE_SYMBOL std::vector<size_t> argsort(const T *arr, \
                                                 size_t arrsize, \
                                                 bool hasnan = false, \
                                                 bool descending = false); \
diff --git a/lib/x86simdsort-scalar.h b/lib/x86simdsort-scalar.h
index 3dc737c..95fab42 100644
--- a/lib/x86simdsort-scalar.h
+++ b/lib/x86simdsort-scalar.h
@@ -71,7 +71,7 @@ namespace scalar {
     }
     template <typename T>
     std::vector<size_t>
-    argsort(T *arr, size_t arrsize, bool hasnan, bool reversed)
+    argsort(const T *arr, size_t arrsize, bool hasnan, bool reversed)
     {
         UNUSED(hasnan);
         std::vector<size_t> arg(arrsize);
diff --git a/lib/x86simdsort-skx.cpp b/lib/x86simdsort-skx.cpp
index 7d9d5aa..f4c4125 100644
--- a/lib/x86simdsort-skx.cpp
+++ b/lib/x86simdsort-skx.cpp
@@ -23,7 +23,7 @@
     } \
     template <> \
     std::vector<size_t> argsort( \
-            type *arr, size_t arrsize, bool hasnan, bool descending) \
+            const type *arr, size_t arrsize, bool hasnan, bool descending) \
     { \
         return x86simdsortStatic::argsort(arr, arrsize, hasnan, descending); \
     } \
diff --git a/lib/x86simdsort.cpp b/lib/x86simdsort.cpp
index 8ef9aad..7aecbea 100644
--- a/lib/x86simdsort.cpp
+++ b/lib/x86simdsort.cpp
@@ -88,11 +88,11 @@ namespace x86simdsort {
 
 #define DECLARE_INTERNAL_argsort(TYPE) \
     static std::vector<size_t> (*internal_argsort##TYPE)( \
-            TYPE *, size_t, bool, bool) \
+            const TYPE *, size_t, bool, bool) \
             = NULL; \
     template <> \
     std::vector<size_t> argsort( \
-            TYPE *arr, size_t arrsize, bool hasnan, bool descending) \
+            const TYPE *arr, size_t arrsize, bool hasnan, bool descending) \
     { \
         return (*internal_argsort##TYPE)(arr, arrsize, hasnan, descending); \
     }
diff --git a/lib/x86simdsort.h b/lib/x86simdsort.h
index e1402fe..c410918 100644
--- a/lib/x86simdsort.h
+++ b/lib/x86simdsort.h
@@ -35,8 +35,10 @@ XSS_EXPORT_SYMBOL void partial_qsort(T *arr,
 
 // argsort
 template <typename T>
-XSS_EXPORT_SYMBOL std::vector<size_t>
-argsort(T *arr, size_t arrsize, bool hasnan = false, bool descending = false);
+XSS_EXPORT_SYMBOL std::vector<size_t> argsort(const T *arr,
+                                              size_t arrsize,
+                                              bool hasnan = false,
+                                              bool descending = false);
 
 // argselect
 template <typename T>
diff --git a/src/README.md b/src/README.md
index 87757b2..2e52a45 100644
--- a/src/README.md
+++ b/src/README.md
@@ -63,7 +63,7 @@ Equivalent to `np.argsort` in
 [NumPy](https://numpy.org/doc/stable/reference/generated/numpy.argsort.html).
 
 ```cpp
-void x86simdsortStatic::argsort<T>(T* arr, size_t *arg, size_t arrsize, bool hasnan = false, bool descending = false);
+void x86simdsortStatic::argsort<T>(const T* arr, size_t *arg, size_t arrsize, bool hasnan = false, bool descending = false);
 ```
 Supported datatypes: `uint32_t`, `int32_t`, `float`, `uint64_t`, `int64_t` and
 `double`.
diff --git a/src/x86simdsort-static-incl.h b/src/x86simdsort-static-incl.h
index 519abe6..852da1f 100644
--- a/src/x86simdsort-static-incl.h
+++ b/src/x86simdsort-static-incl.h
@@ -25,12 +25,14 @@ X86_SIMD_SORT_FINLINE void partial_qsort(T *arr,
                                          bool descending = false);
 
 template <typename T>
-X86_SIMD_SORT_FINLINE std::vector<size_t>
-argsort(T *arr, size_t size, bool hasnan = false, bool descending = false);
+X86_SIMD_SORT_FINLINE std::vector<size_t> argsort(const T *arr,
+                                                  size_t size,
+                                                  bool hasnan = false,
+                                                  bool descending = false);
 
 /* argsort API required by NumPy: */
 template <typename T>
-X86_SIMD_SORT_FINLINE void argsort(T *arr,
+X86_SIMD_SORT_FINLINE void argsort(const T *arr,
                                    size_t *arg,
                                    size_t size,
                                    bool hasnan = false,
@@ -90,14 +92,17 @@ X86_SIMD_SORT_FINLINE void keyvalue_partial_sort(T1 *key,
         ISA##_partial_qsort(arr, k, size, hasnan, descending); \
     } \
     template <typename T> \
-    X86_SIMD_SORT_FINLINE void x86simdsortStatic::argsort( \
-            T *arr, size_t *arg, size_t size, bool hasnan, bool descending) \
+    X86_SIMD_SORT_FINLINE void x86simdsortStatic::argsort(const T *arr, \
+                                                          size_t *arg, \
+                                                          size_t size, \
+                                                          bool hasnan, \
+                                                          bool descending) \
     { \
         ISA##_argsort(arr, arg, size, hasnan, descending); \
     } \
     template <typename T> \
     X86_SIMD_SORT_FINLINE std::vector<size_t> x86simdsortStatic::argsort( \
-            T *arr, size_t size, bool hasnan, bool descending) \
+            const T *arr, size_t size, bool hasnan, bool descending) \
     { \
         std::vector<size_t> indices(size); \
         std::iota(indices.begin(), indices.end(), 0); \
@@ -211,4 +216,4 @@ XSS_METHODS(avx2)
 #error "x86simdsortStatic methods needs to be compiled with avx512/avx2 specific flags"
 #endif // (__AVX512VL__ && __AVX512DQ__) || AVX2
 
-#endif // X86_SIMD_SORT_STATIC_METHODS
+#endif // X86_SIMD_SORT_STATIC_METHODS
\ No newline at end of file
diff --git a/src/xss-common-argsort.h b/src/xss-common-argsort.h
index 7b805fa..9af9e70 100644
--- a/src/xss-common-argsort.h
+++ b/src/xss-common-argsort.h
@@ -675,8 +675,10 @@ X86_SIMD_SORT_INLINE void avx512_argsort(T *arr,
                                          bool hasnan = false,
                                          bool descending = false)
 {
-    xss_argsort<T, zmm_vector, ymm_vector>(
-            arr, arg, arrsize, hasnan, descending);
+    // Safe: argsort never mutates arr; const is dropped only for SIMD type instantiation
+    using base_t = std::remove_const_t<T>;
+    xss_argsort<base_t, zmm_vector, ymm_vector>(
+            const_cast<base_t *>(arr), arg, arrsize, hasnan, descending);
 }
 
 template <typename T>
@@ -686,8 +688,10 @@ X86_SIMD_SORT_INLINE void avx2_argsort(T *arr,
                                        bool hasnan = false,
                                        bool descending = false)
 {
-    xss_argsort<T, avx2_vector, avx2_half_vector>(
-            arr, arg, arrsize, hasnan, descending);
+    // Safe: argsort never mutates arr; const is dropped only for SIMD type instantiation
+    using base_t = std::remove_const_t<T>;
+    xss_argsort<base_t, avx2_vector, avx2_half_vector>(
+            const_cast<base_t *>(arr), arg, arrsize, hasnan, descending);
 }
 
 /* argselect methods for 32-bit and 64-bit dtypes */